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Abstract:

A planar light source device is provided which satisfies the inequality
α1<α2, where α1 is the angle formed between the
direction in which an array of mortar-shaped light-emitting devices (50)
emits light of maximum intensity and a vertical direction on a plane
containing the vertical direction and the X direction or on a plane
containing the vertical direction and the Y direction and α2 is the
angle formed between the direction in which the array of mortar-shaped
light-emitting devices (50) emits light of maximum intensity and a
diagonal direction (C) across the array on a plane containing the
vertical direction and the diagonal direction (C), the first and second
unevenness eliminating sheets (113a and 113b) each having surfaces one of
which is more distant from the light sources than the other and is shaped
such that shapes having upwardly convex cross-sections and extending
along a longitudinal direction are arranged at pitches (P'), the pitches
(Px and Py) being longer than the pitches (P').

Claims:

1. A planar light source device comprising: a plurality of light sources
arrayed at first intervals along a first direction on a mounting
substrate and arrayed at second intervals along a second direction
orthogonal to the first direction; and a plurality of optical sheets
placed in parallel with the mounting substrate at a distance from the
mounting substrate, the light sources each emitting light of maximum
intensity in a direction inclined at an oblique angle with respect to a
direction vertical to a plane on which the light sources are placed, on a
plane containing the vertical direction and the direction along which the
light sources are arrayed, the direction in which the light sources each
emit light of maximum intensity forming an angle α1 with the
vertical direction, on a plane containing the vertical direction and a
diagonal direction across the array of light sources, the direction in
which the light sources each emit light of maximum intensity forming an
angle α2 with the diagonal direction, α1 being less than
α2, the optical sheets each having surfaces one of which is more
distant from the light sources than the other and is shaped such that
shapes having upwardly convex cross-sections and extending along a
longitudinal direction are arranged at third intervals, the first
intervals and the second intervals being longer than the third intervals.

2. The planar light source device as set forth in claim 1, wherein the
first intervals and the second intervals are equal.

3. The planar light source device as set forth in claim 1, wherein the
first intervals are shorter than the second intervals.

4. The planar light source device as set forth in any one of claims 1 to
3, wherein the direction in which the light sources each emit light of
maximum intensity and the vertical direction form an angle of 30 degrees
or larger to 50 degrees or smaller.

5. The planar light source device as set forth in any one of claims 1 to
3, wherein on a virtual view plane parallel to the mounting substrate,
the light sources each has a contour of an illumination profile in a
rectangular shape with rounded vertices.

6. The planar light source device as set forth in claim 5, wherein the
illumination profile has one side parallel to the first direction.

7. The planar light source device as set forth in any one of claims 1 to
6, wherein the first intervals are each 15 mm or longer and a value
obtained by dividing each of the distance by each of the first intervals
is smaller than 0.7.

8. The planar light source device as set forth in any one of claims 4 to
7, wherein each of the light sources is a light source including: a
substrate; a semiconductor light-emitting element die-bonded to the
substrate; and a lens covering the semiconductor light-emitting element,
the lens including (i) four surfaces standing upright with respect to the
substrate and (ii) a ceiling surface right opposite the substrate, the
ceiling surface having a concavely sunken part formed therein.

9. The planar light source device as set forth in claim 8, wherein the
lens serves as a sealing body that seals in the semiconductor
light-emitting element.

10. The planar light source device as set forth in claim 8 or 9, wherein
the sunken part has a circular conical shape, a truncated circular
conical shape, a polygonal conical shape, or a truncated polygonal
conical shape having its vertex pointing to the substrate.

11. The planar light source device as set forth in claim 10, wherein the
semiconductor light-emitting element is placed in an area around a
central axis of the sunken part.

12. The planar light source device as set forth in any one of claims 8 to
11, further comprising a wavelength conversion section, sandwiched
between the semiconductor light-emitting element and the lens, which
covers the semiconductor light-emitting element, the wavelength
conversion section being composed of a resin layer containing a
fluorescent substance dispersed in advance therein, the fluorescent
substance absorbing primary light emitted from the semiconductor
light-emitting element and emitting secondary light.

13. A display device comprising: a planar light source device as set
forth in any one of claims 1 to 12; and a display panel that varies in
light transmission from one pixel to another, the planar light source
device illuminating a back surface of the display panel.

14. A display device as set forth in claim 13, wherein: the display panel
is configured to be able to be driven for each separate region including
the plurality of pixels; and the planar light source device is configured
such that its luminance is able to be adjusted for each separate region
including the plurality of pixels.

Description:

TECHNICAL FIELD

[0001] The present invention relates to a light-emitting device including
a sealing body that directs emitted light in a predetermined direction, a
planar light source device including an array of such light-emitting
devices, and a display device including such a planar light source
device.

BACKGROUND ART

[0002] There has been a liquid crystal display device including, as a
backlight that illuminates the back surface of the liquid crystal display
panel, a planar light source including an array of light sources such as
LEDs (light-emitting diodes). Unlike an edge-light backlight with use of
a light guide plate, such a backlight that illuminates the back surface
of a liquid crystal display panel without use of a light guide plate is
called a direct backlight.

[0003] A challenge to light sources for use in a direct backlight has been
a reduction in the number of light sources for the purpose of cost
reduction, and there has been a need for a special way of expanding
light-distribution characteristics. There have been reports on some
examples of special ways of expanding light-distribution characteristics,
although not disclosed for use as backlight light sources for liquid
crystal display panels.

[0004] Patent Literature 1 discloses, as a conventional technology, an
example of an LED package 30 including an LED chip 38, a lens 32 having a
vertical side wall 35, and an funnel-shaped upper surface 37 (FIG. 21).

[0005] The LED package 30 has two main light paths through which light
travels within the LED package 30. Light that travels through the first
light path P1 is light emitted desirably from the LED chip 38, and
reaches the upper surface 37, which effects total internal reflection
(TIR) that causes the light to exit through the side wall 35 at an angle
of approximately 90 degrees with respect to the vertical axis. Light that
travels through the second light path P2 is (i) light that is emitted
from the LED chip 38 toward the side wall 35 at such an angle that total
internal reflection occurs or (ii) light reflected by the side wall 35 to
exit the LED package 30 at an angle far from being perpendicular to the
vertical axis. The light that travels through the second light path P2 is
not preferable, because it places a limit on the efficiency of extraction
of light through the side wall 35.

[0006] In the example of the LED package 30, it is an object to
efficiently take out light through the side wall 35. Such an object does
not necessarily correspond to the after-mentioned object of the present
application. Further, Patent Literature 1 fails to give a detailed
description of the "lens 32 having a vertical side wall 35" or the
"funnel-shaped upper surface 37".

[0007] Patent Literature 2, which uses an LED in a similar manner to
Patent Literature 1, discloses a LED mounted on a surface to have wide
directivity. Further, Patent Literature 3 discloses a light source, a
light guide, and a planar light-emitting device that can be used in a
railway signal light, a traffic signal light, a large-sized display, a
vehicle's tail light, etc.

[0008] Further, Patent Literatures 4 and 5 each discloses a direct
backlight configured to include an optical sheet by which light from an
arrangement of light sources or from a light source is uniformed in a
plane.

[0014] Although these prior literatures each describes a sealing resin
lens configured to have wide directivity, they fail to describe what
light-distribution characteristics a light-emitting device should have to
serve as a light source for a backlight device that is disposed to face
the back surface of the display panel of a liquid crystal display device
or, in particular, what light-emitting pattern should be formed on a view
plane parallel to the substrate of a light-emitting device.

[0015] Patent Literature 5 discloses light sources each obtained by
covering an LED with a concave lens so that light is emitted from the LED
in a direction at an angle to a direction vertical to a surface on which
the LED has been placed, and discloses uniformizing in-plane luminance by
allowing the light to travel in an oblique direction to enter an optical
sheet disposed to face the light sources.

[0016] However, Patent Literature 5 fails to describe how a distribution
of luminance among the two-dimensional array of light sources along a
diagonal direction is uniformized or how the optical sheet should be
positioned in relation to the light sources from the perspective of the
optical characteristics of the optical sheet for the purpose of reducing
the thickness of the backlight device while improving in-plane
luminance/color unevenness.

[0017] The inventors conducted a detailed study to find that a thin planer
light source device with reduced illuminance unevenness and chromaticity
unevenness can be achieved by rendering the illumination profile
substantially rectangular on a view plane parallel to the substrate of a
light-emitting device. Further, this configuration makes it very easy to
combine separate light-emitting devices in assembling a planer light
source, and if such light-emitting devices are possible, it becomes much
easier to control an area active (local dimming) liquid crystal display
device.

[0018] However, it has been generally believed to be very difficult to
stably obtain a light-emitting device having such a special illumination
profile, i.e., a light-emitting device having a rectangular illumination
profile.

[0019] The present invention has been made in view of the foregoing
problems, and it is an object of the present invention to provide a thin
display device that has little illuminance unevenness or chromaticity
unevenness and a planar light source device structured to be suitable for
such a display device.

Solution to Problem

[0020] In order to solve the foregoing problems, a planar light source
device of the present invention is a planar light source device
including: a plurality of light sources arrayed at first intervals along
a first direction on a mounting substrate and arrayed at second intervals
along a second direction orthogonal to the first direction; and a
plurality of optical sheets placed in parallel with the mounting
substrate at a distance from the mounting substrate, the light sources
each emitting light of maximum intensity in a direction inclined at an
oblique angle with respect to a direction vertical to a plane on which
the light sources are placed, on a plane containing the vertical
direction and the direction along which the light sources are arrayed,
the direction in which the light sources each emit light of maximum
intensity forming an angle α1 with the vertical direction, on a
plane containing the vertical direction and a diagonal direction across
the array of light sources, the direction in which the light sources each
emit light of maximum intensity forming an angle α2 with the
diagonal direction, α1 being less than α2, the optical sheets
each having surfaces one of which is more distant from the light sources
than the other and is shaped such that shapes having upwardly convex
cross-sections and extending along a longitudinal direction are arranged
at third intervals, the first intervals and the second intervals being
longer than the third intervals.

[0021] According to the present invention, the following relationship
between the angle α1 and the angle α2 holds:
α1<α2. Therefore, when the planar light source device is
looked squarely at, light of a predetermined luminance comes also to a
position directly above the vicinity of an area between light sources
adjacent to each other along the diagonal direction. This makes it
possible to reduce luminance unevenness along the diagonal direction.

[0022] Further, the first intervals and the second intervals are longer
than the third intervals. Therefore, the density of the bright and dart
areas can be made higher on a light-emitting pattern as viewed from above
the optical sheets, so that luminance unevenness becomes less
conspicuous. This makes it possible to provide a planar light source
device structured to be suitable for a thin display device that has
little illuminance unevenness or chromaticity unevenness.

Advantageous Effects of Invention

[0023] As described above, the planar light source device of the present
invention is configured such that: the light sources each emit light of
maximum intensity in a direction inclined at an oblique angle with
respect to a direction vertical to a plane on which the light sources are
placed; on a plane containing the vertical direction and the direction
along which the light sources are arrayed, the direction in which the
light sources each emit light of maximum intensity forms an angle
α1 with the vertical direction; on a plane containing the vertical
direction and a diagonal direction across the array of light sources, the
direction in which the light sources each emit light of maximum intensity
forms an angle α2 with the diagonal direction; α1 being less
than α2; the optical sheets each have surfaces one of which is more
distant from the light sources than the other and is shaped such that
shapes having upwardly convex cross-sections and extending along a
longitudinal direction are arranged at third intervals; and the first
intervals and the second intervals are longer than the third intervals.

[0024] This brings about an effect of providing a planar light source
device structured to be suitable for a thin display device that has
little illuminance unevenness or chromaticity unevenness.

BRIEF DESCRIPTION OF DRAWINGS

[0025] FIG. 1 shows explanatory diagrams (a) to (c) explaining a
mortar-shaped light-emitting device according to an embodiment of the
present invention, (a) being a plan view of the mortar-shaped
light-emitting device according to the embodiment of the present
invention, (b) being a front view of the mortar-shaped light-emitting
device according to the embodiment of the present invention, and (c)
being a side view of the mortar-shaped light-emitting device according to
the embodiment of the present invention.

[0026] FIG. 2 shows explanatory diagrams (a) to (e) explaining a
mortar-shaped light-emitting device according to an embodiment of the
present invention, (a) being a plan view showing an internal structure of
the mortar-shaped light-emitting device according to the embodiment of
the present invention, (b) being a front view showing the internal
structure of the mortar-shaped light-emitting device according to the
embodiment of the present invention, (c) being a plan view showing a
central space area and a vertex in the mortar-shaped light-emitting
device according to the embodiment of the present invention, (d) being a
plan view showing one LED chip being die-bonded to a position of
intersection between the substrate and the main axis in the mortar-shaped
light-emitting device according to the embodiment of the present
invention, (e) being a front view showing a preferred height of a sealing
lens in the mortar-shaped light-emitting device according to the
embodiment of the present invention.

[0027] FIG. 3 shows explanatory diagrams (a) to (c) explaining a
mortar-shaped light-emitting device according to an embodiment of the
present invention, (a) being a plan view showing an internal structure of
the mortar-shaped light-emitting device according to the embodiment of
the present invention, (b) and (c) each being an enlarged view of LED
chips and an area therearound in the mortar-shaped light-emitting device
according to the embodiment of the present invention.

[0028] FIG. 4 shows explanatory diagrams (a) to (d) explaining a
mortar-shaped light-emitting device according to an embodiment of the
present invention, (a) being a plan view showing an internal structure of
a modification of arrangement of LED chips in the mortar-shaped
light-emitting device according to the embodiment of the present
invention, (b) to (d) each being an enlarged view of LED chips and an
area therearound in the mortar-shaped light-emitting device according to
the embodiment of the present invention.

[0029] FIG. 5 shows explanatory diagrams (a) to (c) explaining a
mortar-shaped light-emitting device according to an embodiment of the
present invention, (a) being a plan view showing an internal structure of
the mortar-shaped light-emitting device according to the embodiment of
the present invention, (b) and (c) each being an enlarged view of an LED
chip and an area therearound in the mortar-shaped light-emitting device
according to the embodiment of the present invention.

[0030] FIG. 6 shows the light-distribution characteristics (dependence on
the angle of radiation of an intensity distribution of emitted light) of
a mortar-shaped light-emitting device according to an embodiment of the
present invention, the illumination profile (intensity distribution of
emitted light on a virtual view plane) of the mortar-shaped
light-emitting device according to the embodiment of the present
invention, and a method for evaluating the illumination profile of the
mortar-shaped light-emitting device according to the embodiment of the
present invention, (a) being a simulation diagram three-dimensionally
showing the light-distribution characteristics of the mortar-shaped
light-emitting device according to the embodiment of the present
invention, (b) being a graph showing actual measurements of the
light-distribution characteristics (dependence on the angle of radiation
of an intensity distribution of emitted light) of a cross-section
containing the vertical direction and the x direction and a cross-section
containing the vertical direction and the B direction (obtained by
rotating the x direction 45 degrees in the x-y plane), the cross-sections
being cut out of the diagram showing the light-distribution
characteristics of the mortar-shaped light-emitting device according to
the embodiment of the present invention, (c) being a simulation diagram
showing the illumination profile of the mortar-shaped light-emitting
device according to the embodiment of the present invention, (d) showing
the method for evaluating the illumination profile of the mortar-shaped
light-emitting device according to the embodiment of the present
invention.

[0031] FIG. 7 shows the shape, light-distribution characteristics, and
illumination profile of a domed light-emitting device, (a) being a
perspective view of the domed light-emitting device, (b) being a
simulation diagram three-dimensionally showing the light-distribution
characteristics of the domed light-emitting device, (c) being a
simulation diagram showing the illumination profile of the domed
light-emitting device.

[0032] FIG. 8 shows the shape of a cloverleaf light-emitting device, (a)
being a plan view of the cloverleaf light-emitting device, (b) being a
front view of the cloverleaf light-emitting device, (c) being a side view
of the cloverleaf light-emitting device.

[0033] FIG. 9 shows the light-distribution characteristics and
illumination profile of the cloverleaf light-emitting device, (a) being a
simulation diagram three-dimensionally showing the light-distribution
characteristics of the cloverleaf light-emitting device, (b) being a
simulation diagram showing the illumination profile of the cloverleaf
light-emitting device.

[0034] FIG. 10 shows a schematic diagram of a planar light source
according to an embodiment of the present invention, the illumination
profile of a mortar-shaped light-emitting device, and a pattern of
arrangement of mortar-shaped light-emitting devices, (a) being a side
view of a display device according to the embodiment of the present
invention, (b) being a schematic diagram showing correspondence between a
mortar-shaped light-emitting device according to the embodiment of the
present invention and the illumination profile, (c) being a plan view
showing an arrangement of mortar-shaped light-emitting devices according
to the embodiment of the present invention and the illumination profiles
of them as a planar light source, (d) being a perspective view showing an
arrangement of unevenness eliminating sheets and luminance improving
films for use in a planar light source according to the embodiment of the
present invention, (e) being a plan view showing that the busbar
direction of the lens structure of an unevenness eliminating sheet and
the direction of one side of a rectangular light-distribution pattern are
parallel to each other in a planar light source according to the
embodiment of the present invention, (f) being a perspective view
explaining a gap in a light source array along a diagonal direction can
be filled in a planar light source according to the embodiment of the
present invention.

[0035] FIG. 11 shows cases of optical sheets each having a lenticular
structure, (a) and (c) each being a front view showing an arrangement of
a point light source and the optical sheet and the direction of emission
of light, (b) and (d) each being a plan view showing a pattern of
emission as seen from above the optical sheet.

[0036] FIG. 12 shows explanatory diagrams (a) to (c) explaining a
wedge-shaped light-emitting device according to another embodiment of the
present invention, (a) being a plan view of the wedge-shaped
light-emitting device according to the embodiment of the present
invention, (b) being a front view of the wedge-shaped light-emitting
device according to the embodiment of the present invention, and (c)
being a side view of the wedge-shaped light-emitting device according to
the embodiment of the present invention.

[0037] FIG. 13 shows explanatory diagrams (a) to (e) explaining a
wedge-shaped light-emitting device according to another embodiment of the
present invention, (a) being a plan view showing an internal structure of
the wedge-shaped light-emitting device according to the embodiment of the
present invention, (b) being a front view showing the internal structure
of the wedge-shaped light-emitting device according to the embodiment of
the present invention, (c) being a side view of the wedge-shaped
light-emitting device according to the embodiment of the present
invention, (d) being an enlarged view of long LED chips and an area
therearound in the wedge-shaped light-emitting device according to the
embodiment of the present invention, (e) being a plan view showing one
long LED chip being die-bonded to a position directly below the vertex of
the letter V in the wedge-shaped light-emitting device according to the
embodiment of the present invention.

[0038] FIG. 14 shows the light-distribution characteristics and
illumination profile of a wedge-shaped light-emitting device according to
another embodiment of the present invention, (a) being a simulation
diagram three-dimensionally showing the light-distribution
characteristics of the wedge-shaped light-emitting device according to
the embodiment of the present invention, (b) being a simulation diagram
showing the illumination profile of the wedge-shaped light-emitting
device according to the embodiment of the present invention.

[0039] FIG. 15 shows a schematic diagram of a planar light source
according to another embodiment of the present invention and a pattern of
arrangement of wedge-shaped light-emitting devices, (a) being a side view
of a display device according to the embodiment of the present invention,
(b) being a schematic diagram showing correspondence between a
wedge-shaped light-emitting device according to the embodiment of the
present invention and the illumination profile, (c) being a plan view
showing an arrangement of wedge-shaped light-emitting devices according
to the embodiment of the present invention and the illumination profiles
of them as a planar light source, (d) being a perspective view showing an
arrangement of unevenness eliminating sheets and luminance improving
films for use in a planar light source according to the embodiment of the
present invention, (e) being a plan view showing that the busbar
direction of the lens structure of an unevenness eliminating sheet and
the direction of one side of a rectangular light-distribution pattern are
parallel to each other in a planar light source according to the
embodiment of the present invention.

[0040] FIG. 16 shows explanatory diagrams (a) to (d) explaining a
light-emitting device according to still another embodiment of the
present invention, (a) being a plan view showing an internal structure of
the light-emitting device according to the embodiment of the present
invention, (b) being a front view showing the internal structure of the
light-emitting device according to the embodiment of the present
invention, (c) being an enlarged view of LED chips and an area
therearound in the light-emitting device according to the embodiment of
the present invention, (d) being a plan view showing one LED chip being
die-bonded to a position directly below the vertex of the letter V in the
light-emitting device according to the embodiment of the present
invention.

[0041] FIG. 17 shows the light-distribution characteristics and
illumination profile of a light-emitting device according to still
another embodiment of the present invention, (a) being a simulation
diagram three-dimensionally showing the light-distribution
characteristics of the light-emitting device according to the embodiment
of the present invention, (b) being a simulation diagram showing the
illumination profile of the light-emitting device according to the
embodiment of the present invention.

[0042] FIG. 18 shows explanatory diagrams (a) to (d) explaining a
light-emitting device according to still another embodiment of the
present invention, (a) being a plan view of the light-emitting device
according to the embodiment of the present invention, (b) being a front
view of the light-emitting device according to the embodiment of the
present invention, and (c) being a side view of the light-emitting device
according to the embodiment of the present invention, (d) being a side
view of the light-emitting device according to the embodiment of the
present invention as seen from an oblique angle of 45 degrees (from an
angle θa).

[0043] FIG. 19 shows the light-distribution characteristics and
illumination profile of a light-emitting device according to still
another embodiment of the present invention, (a) being a simulation
diagram three-dimensionally showing the light-distribution
characteristics of the light-emitting device according to the embodiment
of the present invention, (b) being a simulation diagram showing the
illumination profile of the light-emitting device according to the
embodiment of the present invention.

[0044] FIG. 20 shows schematic diagrams (a) to (d) showing an area active
(local dimming) liquid crystal display device, (a) being a plan view of
the area active (local dimming) liquid crystal display device, (b) being
a transverse cross-sectional view of the area active (local dimming)
liquid crystal display device as taken along the line A-A', (c) and (d)
showing a positional relationship between regions into which the display
panel has been divided and those into which the planar light source has
been divided.

[0045] FIG. 21 is a front view of a conventional LED package.

[0046] FIG. 22 shows a top view and a side view of a light-emitting device
of Additional Embodiment 1.

[0047] FIG. 23 shows a top view and a side view of a light-emitting device
of Additional Embodiment 2.

DESCRIPTION OF EMBODIMENTS

Embodiment 1

[0048] An embodiment of the present invention is described below with
reference to FIGS. 1 through 10.

[0049] (Light-Emitting Device)

[0050] FIG. 1 shows explanatory diagrams explaining a mortar-shaped
light-emitting device 50 according to Embodiment 1. (a) of FIG. 1 is a
plan view of the mortar-shaped light-emitting device 50 according to
Embodiment 1. (b) of FIG. 1 is a front view of the mortar-shaped
light-emitting device 50 according Embodiment 1. (c) of FIG. 1 is a side
view of the mortar-shaped light-emitting device 50 according to
Embodiment 1.

[0051] FIG. 2 shows explanatory diagrams explaining the mortar-shaped
light-emitting device 50 according to Embodiment 1. (a) of FIG. 2 is a
plan view showing an internal structure of the mortar-shaped
light-emitting device 50 according to Embodiment 1. (b) of FIG. 2 is a
front view showing the internal structure of the mortar-shaped
light-emitting device 50 according to Embodiment 1. (c) of FIG. 2 is a
plan view showing space areas 12a and 12b between four LED chips 12, a
central space area 12c, and a vertex 10c in the mortar-shaped
light-emitting device 50 according to Embodiment 1. The central space
area 12c is an area of overlap between the two space areas 12a and 12b in
(c) of FIG. 12. The space area 12a is a rectangular area which passes
through a point of intersection between a main axis 11 and a surface of a
substrate 20 having a square shape and which, as will be described later,
has its longer sides parallel to and its shorter sides perpendicular to
one side of the substrate 20 when viewed planimetrically. The space area
12b is out of angle with the space area 12a by 90 degrees with the main
axis 11 as a central point of rotation. In Embodiment 1, each of the LED
chips, mounted on the substrate 20, which each have a rectangular shape
when viewed planimetrically, has one side parallel to the longer sides of
the space area 12a or 12b, and the length of each of the shorter sides of
the space area 12a or 12b is equal to the space distance between LED
chips disposed with the space area 12a or 12b therebetween. (d) of FIG. 2
is a plan view showing one LED chip 25 being die-bonded to a position of
intersection between the substrate 20 and the main axis 11 in the
mortar-shaped light-emitting device 50 according to Embodiment 1.

[0052] The mortar-shaped light-emitting device 50 has such features in
appearance that it includes four side surfaces 13a, 13b, 13c, and 13d
that keep in an upright position a sealing lens 10 covering the LED chips
12, that the sealing lens 10 has a top surface 10a having a quadrangular
shape when viewed planimetrically, and that the top surface 10a has a
concavely sunken part located above a substantially central part of the
substrate 20. The concavely sunken part has a substantially conical shape
formed in rotation symmetry about the main axis 11. It should be noted
here that the main axis 11 is the central axis of the shape of the
sealing lens 10 and, in the present invention, coincides with the
arrangement of semiconductor light-emitting elements (hereinafter
referred to as "LED chips 25") to be described later and the central axis
of the illumination profile (intensity distribution of emitted light on a
virtual view plane) of each semiconductor light-emitting element. It
should also be noted that the conical shape may be replaced by a
truncated conical shape, a polygonal conical shape, or a truncated
polygonal conical shape.

[0053] A configuration of the mortar-shaped light-emitting device 50 is
described below. The mortar-shaped light-emitting device 50 includes the
substrate 20, the LED chips 25 die-bonded to the substrate 20, a
wavelength conversion section 40 covering the LED chips 25, and the
sealing lens 10 covering the wavelength conversion section 40. The
sealing lens 10, formed directly on the wavelength conversion section 40,
serves also as a sealing body and, as such, contributes to a reduction in
size of the mortar-shaped light-emitting device 50 and has a sufficient
strength. Alternatively, it is possible to provide a gap between the
sealing lens 10 and the wavelength conversion section 40 (in which case
the lens 10 no longer serves also as a sealing body). In particular, it
is possible to shape the gap in such a way as to adjust
light-distribution characteristics by refracting light.

[0054] For example, the typical dimensions of the mortar-shaped
light-emitting device 50 are as follows: the substrate 20 is 3.2 mm on a
side; the sealing lens 10 is 2.8 mm on a side and 1.6 mm in height; and
each of the LED chips 25 is 0.4 mm on a side and 0.1 mm in height.

[0055] The substrate 20 preferably has a flat surface, is made of a
material such as ceramic, resin, or metal, and has electrodes (not
illustrated) formed on the surface or an inner part thereof to supply
electrical power to the LED chips 25. The LED chips 25 are nitride
semiconductor light-emitting elements and emit primary light which is
blue light having its luminescence peak in a blue light wavelength range
of 400 nm to 500 nm, for example.

[0056] The LED chips 25 are die-bonded to the substrate 20 with brazing
filler metal, an adhesive, or the like, and each have positive and
negative electrodes provided on its surface and electrically connected by
wire bonding to two electrodes (not illustrated) provided on the
substrate 20, respectively. The LED chips 25 can be mounted on the
substrate by flip chip bonding instead of wire bonding. That is, the
positive and negative electrodes formed on the surface of each LED chip
25 can be electrically connected to two electrodes formed on the
substrate surface, respectively, with the surface of each LED chip 25
facing the substrate surface. Alternatively, it is possible to use an LED
chip having positive and negative electrodes disposed on both surfaces
thereof, respectively, in which case the positive electrode can be
connected to an electrode on the substrate by wire bonding and the
negative electrode can be connected to an electrode on the substrate
surface with a conductive bonding material or the like.

[0057] Next, the wavelength conversion section 40 is formed by covering
the LED chips 25 with a resin in which a fluorescent substance has been
dispersed in advance. The fluorescent substance is a substance that
absorbs the primary light emitted by the LED chips 25 and emit secondary
light which is yellow light having its luminescence peak in a yellow
light wavelength range of 550 nm to 600 nm, for example. The
mortar-shaped light-emitting device 50 is configured to emit white light,
which is a mixture of the primary light and the secondary light.

[0059] Further, the LED chips 25, which emit blue light, may be replaced
by LED chips that emit ultraviolet (near-ultraviolet) light having its
luminescent peak wavelength falling within a range of 390 nm to 420 nm.
This brings about a further improvement in luminous efficiency.

[0061] Then, the wavelength conversion section 40 is covered with the
sealing lens 10. The sealing lens 10 is made of a material, such as epoxy
resin or silicone resin, which is capable of transmitting emitted light,
and also functions as a prism that directs emitted light in a
predetermined direction. It should be noted that the wavelength
conversion section 40 may be made of a base material that is either the
same resin as the resin of which the sealing lens 10 is made, or a resin
which is equal in refractive index to or greater in refractive index than
the resin of which the sealing lens 10 is made.

[0062] The sealing lens 10 includes four side surfaces 13a, 13b, 13c, and
13d standing upright, and has a quadrangular contour when viewed
planimetrically. These side surfaces are almost flat, but do not
necessarily need to be completely flat. As shown in (b) and (c) of FIG.
1, each of these side surfaces is not perpendicular to the substrate but
has an inclination that gets nearer slightly to the center as it extends
upward. This brings about such an advantage that it is easy to die-cut
the sealing lens 10 in the case of resin molding of the sealing lens 10
with use of a mold. It should be noted that since light that passes
through the side surface refracts, the illumination profile on a plane at
a given distance from the light-emitting device can be narrowed as a
whole or, on the other hand, the illumination profile can be widened by
appropriately adjusting the slope. Therefore, the angles of inclination
of the side surfaces 13a, 13b, 13c, and 13d are determined in
consideration of broadening of light distribution and uniformity of light
distribution.

[0063] Further, the sealing lens 10 has the top surface 10a, which is
flat, and the sunken part, placed in a central part of the top surface
10a (preferably on the main axis 11), which includes a mortar-shaped (or,
preferably, conical-shaped) slope 10b. It is preferable that the slope
10b have a truncated conical shape, a polygonal conical shape, or a
truncated polygonal conical shape, as well as a conical shape. Further,
the shape of the sunken part does not need to be in axial symmetry about
the main axis 11, and can be changed appropriately for optimization of
the light-distribution characteristics. For ease of production and a
continuous distribution of illumination, it is preferable that a joint
between one of the side surfaces 13a, 13b, 13c, and 13d and another and a
joint between each of them and the ceiling surface 10a be smooth.

[0064] Concern that arises in a case where the light-emitting section is
covered with the sealing lens 10, which is a cuboid sealing resin, is
that the efficiency of extraction of light decreases due to total
reflection that occurs at the boundary surface between an outer surface
of the sealing lens 10 or, in particular, the slope 10b constituting the
sunken part and air. However, as seen in the mortar-shaped light-emitting
device 50 of Embodiment 1, the same level of efficiency of extraction of
light as in the after-mentioned domed light-emitting device 60 can be
achieved by placing, in the central part of the sealing lens 10, a
comparatively large concavely sunken part having an inclined surface and
by setting the height of the sealing lens 10 greater by at least one
third or, more preferably, one half than the width of the sealing lens
10.

[0065] It should be noted here that, as shown in (a) of FIG. 2, a total of
four LED chips 25 are die-bonded to the respective vertices of an
imaginary square 24 centered at the main axis 11 and indicted by a chain
double-dashed line on the surface of the substrate 20. It should also be
noted here that the vertex 10c of the mortar-shaped slope 10b, formed on
the top surface 10a of the sealing lens 10, is in such a position that
the main axis 11 passes through the vertex 10c. Further, the point of
intersection 12 between two lines PP and QQ, indicated by chain
double-dashed lines, which pass through the center of the space area 12a
between two adjacent LED chips 25 and the center of the space area 12b
between two adjacent LED chips 25 is similarly in such a position that
the main axis 11 passes through the point of intersection 12. That is,
when viewed planimetrically in (a) of FIG. 2, the vertex 10c and the
point of intersection 12 coincide substantially with each other.

[0066] Such a configuration allows the position of the vertex 10c as
viewed planimetrically in (c) of FIG. 2 to fall within the central space
area 12 among the LED chips as shown in (c) of FIG. 2 so that the four
LED chips 25 are arranged substantially evenly on all four sides with
respect to the mortar-shaped slope 10b, even if the die-bonding position
of the LED chips 25 is slightly displaced along the x direction or the y
direction or, even if, in the case of molding of the sealing lens 10, the
position of the mortar-shaped slope 10b is slightly displaced along the x
direction or the y direction. For this reason, the resulting
light-distribution characteristics of the mortar-shaped light-emitting
device 50 is stably high in plane symmetry about a plane obtained by
extending the lines PP and QQ along a direction perpendicular to the
substrate.

[0067] More specifically, as shown in (b) of FIG. 2, the mortar-shaped
slope 10b, when viewed in cross-section, is constituted by two slopes
with the vertex 10c interposed therebetween. Therefore, it is necessary
to consider for each separate slope the reflection and refraction
characteristics of incident light emitted by the LED chips 25. In other
words, the two slopes are equal in angle of inclination and therefore
equal in reflection and refraction characteristics with respect to the
angle of incidence of light, but require consideration of the fact that
they are bilaterally symmetrical with each other. In a case where a
single LED chip 25 is placed directly below the vertex 10c, there is an
increase in amount of incident light on that one of the mortar-shaped
slopes directly below which the center of the LED chip 25 comes when the
LED chip 25 shifts in one direction with respect to the vertex 10c,
whereas there is a decrease in amount of incident light on that one of
the mortar-shaped slopes directly below which the center of the LED chip
25 does not come. This is because that one of the mortar-shaped slopes
directly below which the center of the LED chip 25 comes casts a shadow.
As a result, there is likely to be disruption of a balance of extraction
of light between the two slopes. On the other hand, in a case where
separate LED chips are placed directly below the two slopes, light
emitted by the LED chip placed directly below one of the slopes mostly
does not enter the other, thus exerting little influence. Moreover, even
if the LED chip located directly below one of the slopes shifts rightward
or leftward, three will be no change in angle of incidence of light
emitted by the LED chip to the slope, unless the LED chip goes beyond the
vertex 10c, with the slope 10b having a fixed angle of inclination.
Therefore, there will be little disruption of a balance of extraction of
light between the two slopes.

[0068] In summary, in a case where the LED chips, when viewed in
cross-section, are placed together directly below one of the slopes in
avoidance of being directly below the vertex 10c or placed separately
directly below the two slopes, there is unlikely to be disruption of a
balance of extraction of light between the two slopes as the
light-emitting device, even if the LED chips are displaced with respect
to the vertex 10c to such an extent that the LED chips do not pass
transversely across the vertex 10c.

[0069] It should be noted that the foregoing presupposes that the
wavelength conversion section 40 is displaced in accordance with the
displacement of the LED chips 25.

[0070] Further the LED chips 25 are surrounded by the wavelength
conversion section 40 containing the fluorescent substance in the form of
particles. Part (primary light) of the light emitted from the LED chips
25 is absorbed by the fluorescent substance, and the secondary light,
which is longer in wavelength than the primary light, is emitted
isotropically. Another part of the light emitted from the LED chips 25 is
scattered by the fluorescent substance, and still another part of the
light emitted from the LED chips 25 is transmitted without being absorbed
or scattered. Therefore, the particles of the fluorescent substance per
se serve point-like light sources, and it is necessary to consider the
influence exerted thereby. However, emitted light and scattered light
that originate from the particles of the fluorescent substance are
greatly affected by the light emitted from an LED chip located nearer to
the particles of the fluorescent substance, the influence on extraction
of light by displacement of an LED chip tends roughly to be as described
above.

[0071] It should be noted here that the central space area 12c among the
LED chips 25 is an area of intersection between the two space areas 12a
and 12b between the LED chips 25.

[0072] It should be noted that the mortar-shaped light-emitting device 50
may be configured such that, as shown in (d) of FIG. 2, a single LED chip
25 is die-boned to a position of intersection between the substrate 20
and the main axis 11. In this case, it is essential to distribute light
evenly in four directions by strictly managing manufacturing so that the
center of the LED chip 25 intersects with the main axis 11. For this
reason, the degree of difficulty with which products of the same
light-distribution characteristics are stably produced is higher than in
the case where the four LED chips 25 are disposed evenly as shown in (a)
of FIG. 2.

[0073] Further, due to problems of processing accuracy, it is difficult to
make the vertex 10c of the mortar shape in the form of an ideal vertex,
i.e., a sharp-pointed shape, and the placement of an LED chip 25 as shown
in (d) of FIG. 2 causes a problem of leakage of light upward along the
axis. For this reason, it is especially preferable, for realization of
stable characteristics in production, that the mortar-shaped
light-emitting device 50 be structured such that such LED chips 25 as
those shown in (a) of FIG. 2 are arrayed in a position displaced from the
vertex 10c.

[0074] While FIG. 2 has shown a case of arrangement of four LED chips 25,
FIG. 3 shows a case of arrangement of three LED chips. FIG. 3 shows
explanatory diagrams explaining a mortar-shaped light-emitting device 121
according to Embodiment 1. (a) of FIG. 3 is a plan view showing an
internal structure of the mortar-shaped light-emitting device 121
according Embodiment 1. (b) and (c) of FIG. 3 are each an enlarged view
of LED chips and an area therearound in the mortar-shaped light-emitting
device 121 according to Embodiment 1. The LED chips 25 may be arranged as
shown in (c) of FIG. 3, but light distribution is more stable when the
LED chips 25 are arranged as shown in (b) of FIG. 3. Therefore, for the
purpose of production, it is more preferable that the LED chips 25 be
arranged as shown in (b) of FIG. 3.

[0075] FIG. 4 shows explanatory diagrams explaining a mortar-shaped
light-emitting device 122 according to Embodiment 1. (a) of FIG. 4 is a
plan view showing an internal structure of a modification of arrangement
of LED chips in the mortar-shaped light-emitting device 122 according to
Embodiment 1, with two LED chips mounted. (b) to (d) of FIG. 4 are each
an enlarged view of LED chips and an area therearound in the
mortar-shaped light-emitting device 122 according to Embodiment 1, and
each showing the arrangement of LED chips in (a) of FIG. 4 or a
modification of arrangement of LED chips different from that shown in (a)
of FIG. 4.

[0076] In (a) and (b) of FIG. 4, the LED chips are arranged so that each
of the LED chips has one side extending along the same longer side of the
same space area 12b as that shown in FIG. 2, and that each of the LED
chips has another side, orthogonal to that one side, which extends along
the opposite longer sides of the space area 12a, respectively, and that
the space area 12a lies between the LED chips.

[0077] In (c) of FIG. 4, the LED chips are arranged so that each of the
LED chips has one side extending along the opposite longer sides of the
space area 12a or 12b, respectively, and has another side, orthogonal to
that one side, which extends along the opposite longer sides of the space
area 12a or 12b, respectively, that the space area 12a or 12b lies
between the LED chips, that the LED chips get lined up diagonally across
the substrate, and that the LED chips are in centrosymmetry with each
other about the main axis 11.

[0078] In (d) of FIG. 4, the LED chips are arranged so that each of the
LED chips has one side extending along the opposite longer sides of the
space area 12a, respectively, that the space area 12a lies between the
LED chips, and each of the LED chips has another side, orthogonal to that
one side, which is parallel to a line perpendicular to the longer sides
of the space area 12a.

[0079] Furthermore, the LED chips are arranged so that a line passing
through the main axis 11 perpendicularly to the longer sides of the space
area 12a passes through the center of each of the LED chips.

[0080] The LED chips 25 may be arranged as shown in (d) of FIG. 4, but as
shown in (b) of FIG. 2, light distribution is more stable when the LED
chips 25 are arranged as shown in (b) or (c) of FIG. 4. Therefore, for
the purpose of production, it is more preferable that the LED chips 25 be
arranged as shown in (b) or (c) of FIG. 4.

[0081] It should be noted that although each of the LED chips used has a
square shape when viewed planimetrically, each of the LED chips used may
have an oblong shape, and for the purpose of making the wavelength
conversion section 40 smaller, such oblong LED chips 25 may for example
be arranged so that their longer sides run parallel. For example, (d) of
FIG. 3 is a plan view of an example of arrangement of three rectangular
LED chips 25, and (e) of FIG. 3 is a plan view of an example of
arrangement of four rectangular LED chips 25. The LED chips 25 are
arranged in parallel with one another along the line PP that passes
through the center of each of the LED chips 25.

[0082] Further, it is preferable that the wavelength conversion section
40, composed of a translucent resin containing a fluorescent substance
dispersed in advance therein, which covers the LED chips 25 have such a
size that the wavelength conversion section 40 falls within an opening in
the mortar-shaped slope 10b (where the ceiling surface and the slope
meet). This allows a reduction in that component of light from the
wavelength conversion section 40 (i.e., of light emitted by the LED chips
25 and light emitted from the fluorescent substance dispersed in the
wavelength conversion section 40) which exits directly through the
ceiling surface 10a and travels toward an area directly above the
light-emitting device, thus allowing an increase in light that enters the
slope 10b. This allows much of the light to be reflected by the slope 10b
and guided toward the side walls 13a to 13b, thus achieving such a
light-emitting device having wide-angle light-distribution
characteristics as will be shown in (a) and (c) of FIG. 6 later.

[0083] FIG. 5 shows explanatory diagrams explaining a mortar-shaped
light-emitting device 123 according Embodiment 1. (a) of FIG. 5 is a plan
view showing an internal structure of the mortar-shaped light-emitting
device 123 according to Embodiment 1. (b) and (c) of FIG. 5 are each an
enlarged view of an LED chip and an area therearound in the mortar-shaped
light-emitting device 123 according to Embodiment 1. The LED chips 25 may
be placed as shown in (c) of FIG. 5, but light distribution is more
stable when the LED chip 25 is placed as shown in (b) of FIG. 5.
Therefore, for the purpose of production, it is more preferable that the
LED chip 25 be arranged as shown in (b) of FIG. 5.

[0084] The issue of the position of the vertex 10c of the mortar shape
along the horizontal direction of the substrate has been discussed thus
far.

[0085] Next, the position of the vertex 10c of the mortar shape along the
vertical direction of the substrate is discussed with reference to the
front view shown in (b) of FIG. 2. It is desirable that the vertex 10c is
as close as possible to the substrate 20 or the LED chips. Such an
arrangement allows light from the LED chips 25 to be guided by the
mortar-shaped slope 10b more effectively toward the four surfaces
standing upright on the periphery of the sealing lens 10. This is because
of an increase in the solid angle from which the mortar-shaped slope 10b
is looked at from the LED chips 25.

[0086] However, it is desirable that the vertex 10c of the mortar shape
not be in contact with the wavelength conversion section 40. This is
because if the vertex 10c makes contact with or cuts into the wavelength
conversion section 40, which contains the fluorescent substance, light
excited by the fluorescent substance leaks from that part to increase the
intensity of light on the axis.

[0087] In summary, it is desirable that the vertex 10c of the mortar shape
be as close as possible to the substrate to such an extent so not to make
contact with the wavelength conversion section 40.

[0088] FIG. 6 shows the light-distribution characteristics (dependence on
the angle of radiation of an intensity distribution of emitted light) of
the mortar-shaped light-emitting device 50 according to Embodiment 1, the
illumination profile (intensity distribution of emitted light on a
virtual view plane) of the mortar-shaped light-emitting device 50
according to Embodiment 1, and a method for evaluating the illumination
profile of the mortar-shaped light-emitting device 50 according to
Embodiment 1. (a) of FIG. 6 is a simulation diagram three-dimensionally
showing the light-distribution characteristics of the mortar-shaped
light-emitting device 50 according to Embodiment 1, and the intensity of
emitted light is indicated by the distance from the center 11a to an
outer edge surface 56.

[0089] (b) of FIG. 6 is a graph showing actual measurements of the
light-distribution characteristics (dependence on the angle of radiation
of an intensity distribution of emitted light) of a cross-section
containing the vertical direction and the x direction and a cross-section
containing the vertical direction and the B direction (obtained by
rotating the x direction 45 degrees in the x-y plane), the cross-sections
being cut out of the diagram showing the light-distribution
characteristics of the mortar-shaped light-emitting device 50 according
to Embodiment 1. These actual measurements correspond substantially to
the simulation values shown in (a) of FIG. 6.

[0090] The angle of radiation (which is an angle formed with the vertical
direction) at which the relative light intensity takes on a maximum value
is α1, which is a minimum value at the cross-section containing the
vertical direction and the x direction, and α2, which is a maximum
value at the cross-section containing the vertical direction and the B
direction (to be described later), and α2 is greater than α1,
whereby a substantially rectangular illumination profile to be described
later is achieved.

[0091] It should be noted that in (b) of FIG. 6, α1 is equal to 36
degrees and α2 is equal to 42 degrees. Further, the B direction is
a diagonal direction across the rectangular illumination profile, and
assuming that the rectangular shape is in the form of a square shape, the
B direction is a direction obtained by rotating the x direction 45
degrees in the x-y plane.

[0092] (c) of FIG. 6 is a simulation diagram showing the illumination
profile of the mortar-shaped light-emitting device 50 according to
Embodiment 1. The term "illumination profile" here means an illumination
profile obtained by illuminating a diffusing plate 112 as will be
described later, and in (c) of FIG. 6, the chain double-dashed line
indicates a contour line 58. As shown in (c) of FIG. 6, the illumination
profile of the mortar-shaped light-emitting device 50 is nonconcentric
and nonaxisymmetric and, in particular, forms a substantially rectangular
(hereinafter simply referred to as "rectangular") illumination profile on
the diffusing plate 112. In other words, there are four bright portions
distributed along the B direction (diagonal direction).

[0093] (d) of FIG. 6 shows the method for evaluating the illumination
profile of the mortar-shaped light-emitting device 50 according to
Embodiment 1. The mortar-shaped light-emitting device 50 is mounted on a
mounting substrate 110, with the diffusing plate 112 disposed to face the
mounting substrate 110. When the mortar-shaped light-emitting device 50
illuminates the back surface of the diffusing plate 112, the illumination
profile is observed on the front surface of the diffusing plate 112.

[0094] It should be noted that observations are made with a distance d of
18 mm from the mounting substrate 110 to the diffusing plate 112.

[0095] The illumination profile here indicates an intensity distribution
of emitted light on a vertical view plane immediately before incidence on
the diffusing plate 112. Meanwhile, the simulation diagram shown in (c)
of FIG. 6 to show the illumination profile described in the present
embodiment is one obtained by simulating an illumination profile on a
view plane immediately before incidence on the diffusing plate 112.

[0096] For comparison, FIG. 7 shows the shape, light-distribution
characteristics, and illumination profile of a domed light-emitting
device. (a) of FIG. 7 is a perspective view of the domed light-emitting
device 60, which includes a substrate 20, an LED chip 25 (not
illustrated) die-bonded to the substrate 20, a wavelength conversion
section 40 covering the LED chip 25; and a domed sealing body 61 covering
the wavelength conversion section 40.

[0097] (b) of FIG. 7 is a simulation diagram three-dimensionally showing
the light-distribution characteristics of the domed light-emitting device
60, and (c) of FIG. 7 is a simulation diagram showing the illumination
profile of the domed light-emitting device 60. These drawings show that
the light-distribution characteristics of the domed light-emitting device
60 exhibits a spherical shape in the three-dimensional simulation diagram
and the illumination profile is concentric with respect to a bright
portion 52 appearing above the LED chip 25.

[0098] A comparison between the illumination profile of the mortar-shaped
light-emitting device 50 and the illumination profile of the domed
light-emitting device 60 shows that the mortar-shaped light-emitting
device 50 illuminates a wider area than the domed light-emitting device
60 does.

[0099] For comparison, FIGS. 8 and 9 shows the shape, light-distribution
characteristics, and illumination profile of a cloverleaf light-emitting
device 70. (a) of FIG. 8 is a plan view of the cloverleaf light-emitting
device 70. (b) of FIG. 8 is a front view of the cloverleaf light-emitting
device 70. (c) of FIG. 8 is a side view of the cloverleaf light-emitting
device 70.

[0100] The cloverleaf light-emitting device 70 includes a substrate 20,
four LED chips 25 die-bonded to the substrate 20, a wavelength conversion
section 40 covering the LED chips 25 and containing a fluorescent
substance dispersed therein, a block-like sealing body (sealing lens) 71
having four raised parts 80a covering the wavelength conversion section
40. As shown in the plan view of (a) of FIG. 8, the four raised parts 80a
are formed by forming groove-like depressed parts 80b respectively
extending vertically and horizontally. The depressed parts 80b are also
shown in the front view of (b) of FIG. 8 and the side view of (c) of FIG.
8. Although the raised parts 80a gently slope down toward the four
vertices of the cloverleaf light-emitting device 70 when viewed
planimetrically, the raised parts 80a may be flat.

[0101] (a) of FIG. 9 is a simulation diagram three-dimensionally showing
the light-distribution characteristics of the cloverleaf light-emitting
device 70. (b) of FIG. 9 is a simulation diagram showing the illumination
profile of the cloverleaf light-emitting device 70. These drawings show
that the illumination profile of the cloverleaf light-emitting device 70
is indicated by a contour line 78 indicated by a chain double-dashed line
in (b) of FIG. 9, that those bright portions surrounded by the contour
line 78 are bright portions 72 that are high in illuminance, and that
those dark portions distributed near the bright portions 72 are dark
portions 74 that are low in illuminance.

[0102] Thus, the illumination profile of the cloverleaf light-emitting
device 70 is such that the four bright portions 72 and the four dark
portions 74 are distributed in positions above the raised part 80a and
positions above the depressed parts 80b, respectively. As a result, the
illumination profile of the cloverleaf light-emitting device exhibits the
shape of the letter X with four-fold symmetry about the center 81a, as
with the shape of the sealing body 71.

[0103] A comparison between the illumination profile of the mortar-shaped
light-emitting device 50 and the illumination profile of the cloverleaf
light-emitting device 70 shows that the cloverleaf light-emitting device
70 also illuminates those parts where the four dark portions 74 are
formed. To the extent that the parts corresponding to the four dark
portions 74 become brighter, the parts corresponding to the four bright
portions 72 decrease in illuminance. As a result, the mortar-shaped
light-emitting device 50 achieves such a substantially rectangular
illumination profile that the parts corresponding to the four bright
portions 72 in the illumination profile of the cloverleaf light-emitting
device 70 serve as vertices.

[0104] It should be noted that although the sealing lens (mortar-shaped
lens) 10 of the mortar-shaped light-emitting device 50 also serves to
seal in the LED chips 25 and the wavelength conversion section 40, it is
also possible to provide a mortar-shaped lens separately from a sealing
body and mount it on an ordinary LED chip sealing body. In so doing, it
is preferable, for the purpose of increasing the efficiency of extraction
of light, that the space between the sealing body and the mortar-shaped
lens be filled with another transparent resin or the like. However, it is
also possible to provide the space without filling it with anything.

[0105] But yet, for the sake of simplicity of manufacture such as the
capabilities of easily positioning the lens with high accuracy,
increasing the efficiency of extraction of light, and finishing lens
fabrication and resin sealing at the same time, it is most preferable
that the mortar-shaped lens serves also as a sealing body as shown in
Embodiment 1.

[0106] It should be noted that it is desirable that the angle of
inclination θ of the mortar-shaped slope 10b be steeper than the
critical angle θc of total reflection. Furthermore, it is desirable
that the angle of inclination θ of the mortar-shaped slope 10b
range from an angle approximately equal to the critical angle θc to
60 degrees. The term "total reflection" here assumes total reflection
that occurs at the boundary between the sealing resin and the atmosphere,
and in a case where the refractive index of the sealing resin is n, the
critical angle θc of total reflection can be calculated according
to arcsin (1/n). By increasing the angle of inclination θ of the
mortar-shaped slope 10b to θc or lager, strong light emitted upward
along the axis of each LED chip 25 or toward an area therearound can be
effectively guided toward the four surfaces standing upright on the
periphery of the sealing lens 10, and light having passed through these
surfaces contributes to the formation of a substantially rectangular
illumination profile.

[0107] On the other hand, if the angle of inclination θ is 60
degrees or larger, more components of the light emitted upward along the
axis of each LED chip 25 are reflected by the slope and emitted toward
the top surface 10a, and therefore can no longer be effectively guided
toward the four surfaces standing upright on the periphery of the sealing
lens 10. For this reason, even if the illumination profile is
rectangular, it is no longer possible to obtain a sufficient area of
illumination. Moreover, for entire coverage of the LED chips 25, an
increase in the angle of inclination of the mortar-shaped slope leads to
an increase in depth of the sunken part and an increase in height of the
device, thus making fabrication difficult.

[0108] For this reason, it can be said to be desirable that the angle of
inclination θ of the mortar-shaped slope 10b range from an angle
approximately equal to the critical angle θc of total reflection to
60 degrees. In the case of use of a typical resin having a refractive
index n of 1.5, the critical angle θc is 41.8 degrees.

[0109] Although the action of the slope 10b has been described mainly in
terms of total reflection, the transmitted components also play an
important role. Part of light emitted from the LED chips 25 or the
wavelength conversion section 40 is transmitted through the slope 10b and
the ceiling surface 10a toward an area directly above the LED chips 25 or
the wavelength conversion section 40, or is transmitted with some
refraction. This causes light to be distributed over an area directly
above the main axis 11, and as shown in (a) and (c) of FIG. 6, the
light-emitting device has such light-distribution characteristics that
light is emitted widely over a predetermined large range of angles of
inclination from a position directly above the main axis 11. Further, in
order that light entering the ceiling surface 10a is refracted to change
from traveling toward an area directly above the LED chips 25 or the
wavelength conversion section 40 to traveling in an oblique direction and
is extracted out of the sealing lens, it is preferable that the ceiling
surface 10a be an optically flat plane. It should be noted that the slope
does not need to be flat when viewed in cross-section and may be curved
when viewed in cross-section.

[0110] As mentioned earlier, it is desirable that the vertex 10c of the
mortar shape be as close as possible to the substrate to such an extent
so not to make contact with the wavelength conversion section 40. At the
same time, it is desirable that the angle of inclination θ of the
mortar-shaped slope 10b range from an angle approximately equal to the
critical angle θc of total reflection to 60 degrees. In view of
both of these in combination, an upper limit to the desirable height (H
in (e) of FIG. 2) of the sealing lens 10 determines itself with respect
to the width W of the sealing lens 10.

[0111] In a case where the mortar-shaped slope 10b is made as wide as
possible, its depth (H0 in (e) of FIG. 2) is approximately 0.45 to 0.86
times as great as the width (W in (e) of FIG. 2) of the sealing lens 10.
According to (e) of FIG. 2, H0 is determined by Wtan θ/2. It should
be noted here that H0/W was calculated based on the fact that a desirable
value of θ ranges from the critical angle θc (which is 41.8
degrees when n=1.5) to 60 degrees. Therefore, the upper limit to the
desirable height (H in (e) of FIG. 2) of the sealing lens 10 can be said
to be a height (H0 in (e) of FIG. 2) calculated from the value of H0/W in
view of the distance between the substrate 20 and the vertex 10c of the
mortar shape in a case where the vertex 10c is located as close as
possible to the substrate to such an extent as not to make contact with
the wavelength conversion section 40.

[0112] More specifically, an example of the typical dimensions of the
mortar-shaped light-emitting device 50 as described above where the
sealing lens 10 is 2.8 mm (which corresponds to W in (e) of FIG. 2) is
now discussed. A typical case is discussed where the thickness of the
wavelength conversion section 40, which covers the LED chips 25, along a
direction perpendicular to the substrate is 0.3 mm (h1 in (e) of FIG. 2)
and the distance (h2 in (e) of FIG. 2) from the wavelength conversion
section 40 to the vertex 10c is 0.1 mm. In this case, the distance H1
between the substrate 20 and the vertex 10c is 0.4 mm, which is 0.14
times as great as the width of 2.8 mm of the sealing lens 10. Therefore,
in this typical example, the upper limit to the desirable height (H in
(e) of FIG. 2) of the sealing lens 10 can be said to range roughly from
0.6 to 1.1 times as great as the width of the sealing lens 10.

[0113] (Planar Light Source)

[0114] FIG. 10 shows a schematic diagram of a planar light source (planar
light source device) 100 according to Embodiment 1, the illumination
profile of each mortar-shaped light-emitting device 50, and a pattern of
arrangement of mortar-shaped light-emitting devices 50. (a) of FIG. 10 is
a side view of a display device 100 including a planar light source 100
and a liquid crystal panel 150. As shown in (a) of FIG. 10, the planar
light source 100 includes a mounting substrate 110, a plurality of
mortar-shaped light-emitting devices 50 disposed on the mounting
substrate 110, and a group of optical sheets 113 put on top of one
another in parallel with a surface of the mounting substrate 110 to face
the mounting substrate 110. That one of the group of optical sheets 113
which is closest to the mortar-shaped light-emitting devices 5 has a
surface facing the mortar-shaped light-emitting devices 5, and the
distance between this surface and the surface of the mounting substrate
110 is d. Light emitted from the mortar-shaped light-emitting devices 50
illuminates the back surface of the group of optical sheets 113, is
uniformly distributed by the group of optical sheets 113, is focused
toward the front surface within a predetermined angle, and is emitted in
the form of planar light through the front surface. It should be noted
that the liquid crystal panel 150 is configured to be able to be driven
for each separate region including a plurality of pixels, and that the
planar light source 100 is configured such that its luminance can be
adjusted for each separate region including the plurality of pixels.

[0115] Each of the mortar-shaped light-emitting devices 50 has its maximum
angle of radiation α1 or α2 in an oblique direction in terms
of a distribution of angles of radiation, but since such an oblique
direction is distant from the light source, the mortar-shaped
light-emitting device 50 still has its maximum luminance directly above
the light source in terms of a distribution of illumination. As will be
mentioned later, the optical sheets serve to reduce luminance by
directing light back to the light source directly above the light source,
increase luminance by directing light upward when the light is away from
the light source, and thereby achieve a uniform distribution of light.

[0116] For a higher reflectance, the mounting substrate has its surface
painted in white or mounted with a reflecting sheet (not illustrated)
provided with a hole through which a mounting part of the mortar-shaped
light-emitting device 50 passes.

[0117] (b) of FIG. 10 is a schematic diagram showing correspondence
between a mortar-shaped light-emitting device 50 and its illumination
profile. The sealing lens 10 of the mortar-shaped light-emitting device
50 has a mortar-shaped slope 10b in its central part when viewed
planimetrically, and the illumination profile 58 on a surface of that one
of the group of optical sheets 113 which is closest to the mortar-shaped
light-emitting device opposite the liquid crystal panel is a
substantially rectangular shape having its vertices diagonally across the
sealing lens 10.

[0118] (c) of FIG. 10 is a plan view showing an arrangement of
mortar-shaped light-emitting devices 50 and the illumination profiles of
them as a planar light source. On the mounting substrate 110, as shown in
(c) of FIG. 10, mortar-shaped light-emitting devices 50 each having such
an illumination profile as shown in (b) of FIG. 10 are squarely arrayed
so that the rectangular illumination profile has one end substantially
parallel to either of the array directions. That is, as indicated by
chain double-dashed lines in (c) of FIG. 10, lattice points at which one
array axis 114 intersects with another form vertices of squares, and the
mortar-shaped light-emitting devices 50 are arrayed so as to be located
on the respective lattice points. Further, the mortar-shaped
light-emitting devices 50 are arrayed at pitches of Px (=P) along the x
direction and at pitches of Py (=P) along the y direction. Such a simple
square arrangement of mortar-shaped light-emitting devices 50 each having
a rectangular illumination profile makes it easy to obtain a planar light
source that is high in in-plane uniformity of illuminance.

[0120] Furthermore, for minimization of an overlap between the
illumination patterns of adjacent mortar-shaped light-emitting devices
50, (i) the pitches P at which the mortar-shaped light-emitting devices
50 are arrayed and (ii) the distance d between the surface, which faces
the mortar-shaped light-emitting devices 50, of the optical sheet which
is closest to the mortar-shaped light-emitting devices 50 and the surface
of the mounting substrate on which the mortar-shaped light-emitting
devices 50 are placed are appropriately set ((a) of FIG. 10).

[0121] That is, the mortar-shaped light-emitting devices 50 are arranged,
without rotating the main axis 11 of FIG. 2, so that as viewed from
above, the quadrangular shape of each of the sealing lens 10 has one side
parallel to either of the array directions.

[0122] With this arrangement, the rectangular illumination patterns of
mortar-shaped light-emitting devices 50 adjacent to each other along the
diagonal direction across the square arrangement of mortar-shaped
light-emitting devices 50 can fill a gap in the surface, so luminance
unevenness can be reduced. In such a rectangular illumination pattern,
when three-dimensionally viewed as the light-distribution characteristics
of the mortar-shaped light-emitting devices 50 as shown in (f) of FIG.
10, the following relationship holds: α1<α2, where
α1 is the angle formed by the direction of emission of light at the
maximum intensity and the main axis in a plane containing either of the
array directions (i.e., either of the x and y directions) of the
mortar-shaped light-emitting devices 50 and the main axis 11 of each of
the mortar-shaped light-emitting devices 50, and α2 is the angle
formed by the direction of emission of light at the maximum intensity and
the main axis in a plane containing the diagonal direction across the
array of mortar-shaped light-emitting devices 50 and the main axis of
each of the mortar-shaped light-emitting devices 50.

[0123] In this case, it is necessary that the illumination profile is more
protruding along the diagonal direction across the light source array
than along the array directions (i.e., the x and y directions). By
satisfying this condition, a gap in the light source array along the
diagonal direction can be filled, so luminance unevenness along the
diagonal direction can be reduced.

[0124] As an example of the present embodiment, each of the pitches Px and
Py of the square arrangement was 45 mm, and the distance d between the
surface of the mounting substrate 110 and that surface of the optical
sheet closest to the mortar-shaped light-emitting devices 50 which faces
the mortar-shaped light-emitting devices 50 was 22 mm. Light emitted from
the mortar-shaped light-emitting devices 50 is emitted in such a way as
shown in (a) of FIG. 6 to have a peak sticking out along the main axis
11. At the same time, the direction of emission of light of maximum
intensity is distributed in such a way that the light of maximum
intensity is emitted in a direction inclined at 45 degrees to the main
axis 11 to surround the main axis 11.

[0125] With such a distribution of the direction of emission of light, the
mortar-shaped light-emitting devices 50 not only illuminate those
positions on the group of optical sheets 113 which are directly above the
mortar-shaped light-emitting devices 50, but also illuminate those
positions on the group of optical sheets 113 which are above spaces
between the mortar-shaped light-emitting devices 50. This contributes to
an improvement in luminance unevenness in those positions on the group of
optical sheets 113 which are above spaces between the mortar-shaped
light-emitting devices 50. The angle of the direction of emission of
light of maximum intensity with respect to the main axis 11 can be
changed by adjusting the shape of each of the sealing lens 10. For
reduction in luminance unevenness and color unevenness, it is desirable
that the angle be 30 to 50 degrees, as long as the angle is in the
after-mentioned range of relationship with the pitches Px and Py and the
distance d.

[0126] Specific examples of the optical sheets put on top of one another
includes first and second unevenness eliminating sheets 113a and 113b put
on top of each other. The first unevenness eliminating sheet 113a is
located closer to the mortar-shaped light-emitting devices 50 than the
second unevenness eliminating sheet 113b is.

[0127] As shown in (d) of FIG. 10, the first unevenness eliminating sheet
113a and the second unevenness eliminating sheet 113b are each an optical
sheet composed of a translucent member whose surface has a lenticular
structure. The luminance and color unevenness of light entering the
optical sheet are corrected along the direction along which convex shapes
are arrayed. It should be noted that the pitches at which the convex
shapes are arrayed are smaller than the pitches at which the
mortar-shaped light-emitting devices 50 are arrayed.

[0128] The term "lenticular structure" above means a surface shape, such
as the one disclosed in Japanese Patent Application Publication,
Tokukaihei, No. 6-194651 A (1994), which has a plurality of partially
(semi)circular long convex shapes, arrayed in parallel at pitches P',
each of which has a cross-section containing part of an ellipse or a
circle. The focusing and dispersion characteristics of the lenticular
structure are adjusted in accordance with the light-distribution
characteristics of the planar light source according to the present
embodiment, and the dimensions are not necessarily the same as those
disclosed in Japanese Patent Application Publication, Tokukaihei, No.
6-194651 A (1994).

[0129] The reason why the convex shapes are arrayed at smaller pitches
than the mortar-shaped light-emitting devices 50 is explained here with
reference to FIG. 11.

[0130] FIG. 11 shows cases of optical sheets 1124 each having a lenticular
structure (lenticular lens structure), (a) and (c) each being a front
view showing an arrangement of a point light source 1121 and the optical
sheet 1122 and the direction of emission of light, (b) and (d) each being
a plan view showing a pattern of emission as seen from above the optical
sheet 1122.

[0131] The optical sheet 1124 is either a first or second unevenness
eliminating sheet 113a or 113b. Further, as shown in (d) of FIG. 11, the
optical sheet 1124 has a lenticular structure whose surface shape has a
plurality of partially (semi)circular long convex shapes, arrayed in
parallel at pitches P', each of which has a cross-section containing part
of an ellipse or a circle. Furthermore, the optical sheet 1124 has a
bottom surface 1125 as shown in (a) and (c) of FIG. 11. FIG. 11 takes
into consideration the refraction of light on the bottom surface 1125.

[0132] First, as shown in (a) and (c) of FIG. 11, light entering the
lenticular structure of the optical sheet 1124 at a critical angle
βc or smaller is reflected inward without being extracted upward
(see the shaded areas 201 (dark areas) in the drawings. As indicted by a
dotted arrow, light entering such an area is reflected by a concavely
curved surface and also reflected by an opposite curved surface to travel
downward). Light entering at an angle larger than the critical angle
βc is extracted upward (see the areas 202 (bright areas) in the
drawings. Light entering such a region is refracted to be extracted
upward).

[0133] Further, as shown in (a) and (b) of FIG. 11, in a case where the
width of each separate bright or dark area is greater and the density of
the bright and dart areas are lower, luminance unevenness is more
conspicuous.

[0134] On the other hand, as shown in (c) and (d) of FIG. 11, in a case
where the width of each separate bright or dark area is smaller and the
density of the bright and dart areas are higher, luminance unevenness
becomes less conspicuous.

[0135] For such a reason, the convex shapes of the first and second
unevenness eliminating sheets 112a and 112b arrayed at the pitches P'
that are smaller than the pitches Px and Py at which the mortar-shaped
light-emitting devices 50 are arrayed.

[0136] It should be noted that in such a position that is above a space
between one point light source (LED light source, which is a
mortar-shaped light-emitting device 50 in this example) 1121 and another,
not in a position that is directly above a point light source 1121, the
angle of incidence is more oblique so that light is likely to enter at an
angle larger than the angle of total reflectance (critical angle
βc). Therefore, the dark areas tend to become smaller in width.

[0137] The foregoing unevenness eliminating sheets are just an example of
unevenness eliminating sheets. As long as the desired focusing and
dispersion characteristics are obtained for elimination of luminance
unevenness, the lenticular structure may have long convex shapes each
having a triangular cross-section.

[0138] The first unevenness eliminating sheet 113a is placed so that the
longitudinal direction (referred to also as "busbar direction") of the
convex shapes of the first unevenness eliminating sheet 113a and the
direction of one side of the substantially rectangular illumination
profile of each of the mortar-shaped light-emitting devices 50 are
parallel to each other, whereby luminance unevenness and color unevenness
along the X direction are uniformized. In practice, the first unevenness
eliminating sheet 113a is placed so that the longitudinal direction of
the convex shapes of the first unevenness eliminating sheet 113a and one
side of the rectangular contour of the sealing resin of each of the
mortar-shaped light-emitting devices 50 as seen from above are parallel
to each other. Alternatively, the first unevenness eliminating sheet 113a
is placed so that the longitudinal direction of the convex shapes of the
first unevenness eliminating sheet 113a and one side of the rectangular
contour of the mounting substrate 110 when the mortar-shaped
light-emitting devices 50 are seen from above are parallel to each other.
Alternatively, the first unevenness eliminating sheet 113a is placed so
that the longitudinal direction of the convex shapes of the first
unevenness eliminating sheet 113a and the X direction along which the
mortar-shaped light-emitting devices 50 are arrayed are parallel to each
other. In other words, as shown in (e) of FIG. 10, the first unevenness
eliminating sheet 113a is placed so that the busbar direction D of the
lens structure of the first unevenness eliminating sheet 113a and the
direction E of one side of the illumination profile (contour of the
sealing resin of the package (whose peripheral border is rectangular as
seen from above)) are placed substantially in parallel with each other.

[0139] The second unevenness eliminating sheet 113b is placed on the first
unevenness eliminating sheet 113a so that the longitudinal direction of
the convex shapes of the second unevenness eliminating sheet 113b is
substantially perpendicular to the longitudinal direction of the convex
shapes of the first unevenness eliminating sheet 113a. That is, the
second unevenness eliminating sheet 113b is placed so that the
longitudinal direction of the convex shapes of the second unevenness
eliminating sheet 113b is parallel to the direction of another side of
the substantially rectangular illumination profile of each of the
mortar-shaped light-emitting devices 50 that is substantially
perpendicular to the one side mentioned above, whereby luminance
unevenness and color unevenness along the Y direction are uniformized.

[0140] It should be noted that luminance unevenness and color unevenness
along a diagonal direction across each substantially rectangular
illumination profile is uniformized by appropriately adjusting the
intervals at which the mortar-shaped light-emitting devices 50 are
arrayed, in addition to using the two unevenness eliminating sheets as
described above. This causes the luminance unevenness and the color
unevenness to be better uniformized by a combined effect of overlapping
of rectangular illumination patterns of mortar-shaped light-emitting
devices 50 adjacent to one another along the X direction, the Y
direction, and the diagonal direction.

[0141] It should be noted that in order to eliminate persistent luminance
and color unevenness, it is possible to further put unevenness
eliminating sheets of the X and Y directions on each of the unevenness
eliminating sheets. Further, in order to save on one unevenness
eliminating sheet, the intervals at which the mortar-shaped
light-emitting devices 50 are arrayed along the X or Y direction may be
narrowed (the square arrangement may be changed to a rectangular
arrangement) so that the unevenness is eliminated by increasing
overlapping of the illumination profiles of mortar-shaped light-emitting
devices 50 adjacent to one another along either of the directions. This
makes it only necessary to provide an unevenness eliminating sheet of the
other direction.

[0142] Further, in order to guide light upward, it is possible to provide
luminance improving films 113c and 113d between the unevenness
eliminating sheets and the liquid crystal panel. The luminance improving
films 113c and 113d, which are commonly known, are optical sheets that
have convex shapes similar to those of the aforementioned unevenness
eliminating sheets but differ more or less in shape from the
aforementioned unevenness eliminating sheets. For example, the convex
shapes of the luminance improving films 113c and 113d are arrayed at
intervals different from those at which the concaves shapes of the
aforementioned unevenness eliminating sheets are arrayed, or the convex
shapes of the luminance improving sheets 113c and 113d each have a
cross-section configured to have a plurality of triangles overlapped with
each other. Further, the luminance improving films have a focusing
function by which light entering the luminance improving films through
their lower surfaces is extracted as upward light within a predetermined
angle. Light other than the light extracted upward is returned toward the
housing by reflection, reflected by the housing, allowed to reenter the
luminance improving films 113c and 113d, and recycled to be extracted
upward, thus increasing frontal luminance. The luminance improving films
have an effect of reducing luminance unevenness along a direction
perpendicular to the longitudinal direction of the convex shapes,
although not comparable to the unevenness eliminating films. As such,
luminance improving films may be used to replace the unevenness
eliminating sheet (i.e., the two films for use in elimination of
unevenness along the X and Y directions) to be put on top of the second
unevenness eliminating sheet.

[0143] It should be noted that in consideration of the unevenness
eliminating effect, the aforementioned pitches Px and Py and distance d
are adjusted to satisfy d/P<0.7, where P denotes the pitches Px and
Py.

[0144] When the distance d is set large or the pitches P are set small so
that d/P 0.7, an increase in overlapping of the illumination profiles of
adjacent light-emitting devices leads to an increase in luminance in a
space between the light-emitting devices, thus making luminance
unevenness likely to occur. Further, as for the pitches P, it is
preferable that P≧15 mm. There are two reasons for this. One of
the reasons is that in a case where the pitches P are too small, there
occurs too much interference between the illumination profiles of
adjacent light-emitting devices, with the result that the unevenness
eliminating sheets no longer exert their effects. The other reason is
that the number of light-emitting devices should be reduced from a cost
standpoint.

[0145] Further, in a case where the mortar-shaped light-emitting devices
50 are arranged in the form of an oblong shape, e.g., so that the pitches
Py along the y direction are smaller than the pitches Px along the x
direction, it is preferable, for the same reasons as those stated above,
that the pitches Px and Py and the distance d be adjusted to satisfy
Px≧15 mm and d/Px<0.7.

[0146] It should be noted that the mortar-shaped light-emitting devices 50
may be replaced by light-emitting devices of another sealing resin
configuration as shown in embodiments other than the present embodiment,
as long as the latter light-emitting devices each have a substantially
rectangular illumination profile.

[0147] Further, the substantially rectangular illumination profile may
have its corners slightly protruding diagonally, albeit not as protruding
diagonally as in the X-shaped illumination profile of the cloverleaf
light-emitting device 70 shown in (c) of FIG. 7.

[0148] Further, since each of the mortar-shaped light-emitting devices 50
illuminates a wider area than does any one of the domed light-emitting
devices 60, the number of light-emitting devices can be reduced when a
planar light source is constituted by a plurality of mortar-shaped
light-emitting devices 50. Further, since each of the mortar-shaped
light-emitting devices 50 emits light at a high angle of emission, i.e.,
emits light nearly in a direction parallel to the mounting substrate 110,
the distance from the mounting substrate 110 to the group of optical
sheets 113 can be made smaller, which gives an advantage in terms of
reduction in thickness of the backlight.

[0149] Further, the mortar-shaped light-emitting devices 50 are much
simpler than the cloverleaf light-emitting devices 70 in that the
mortar-shaped light-emitting devices 50 each have a substantially
rectangular illumination profile. For this reason, unlike the cloverleaf
light-emitting devices 70, the mortar-shaped light-emitting devices 50 do
not need to be specially arranged in consideration of overlap between
bright and dark portions of the illumination profiles for in-plane
uniformity of illuminance.

That is, the mortar-shaped light-emitting devices 50 do not need to be
placed with their main axes rotated in accordance with the illumination
profiles, nor do they need to be arranged in a houndstooth pattern. This
makes it possible to greatly simplify the design and production of a
planar light source. Furthermore, this makes it possible to greatly
simplify the design and production of a backlight to be provided in an
area active (local dimming) display device to be described later.

[0150] It should be noted that although the term "rectangular shape" in
the present embodiment refers to a square or an oblong shape, but its
contour, including the vertices, may be rounded and curved. The term
"curve" encompasses a mixture of slightly concave and convex curves
smoothly combined, as seen from outside of the rectangular shape.

Embodiment 2

[0151] Another embodiment of the present invention is described below with
reference to FIGS. 12 through 15. It should be noted that the present
embodiment is identical in configuration to Embodiment 1 except for that
which is described in the present embodiment. Further, for convenience of
explanation, members having the same functions as those shown in the
drawings of Embodiment 1 are given the same reference numerals and, as
such, are not described below.

[0152] FIG. 12 shows a plan view, a front view, and a side view of a
wedge-shaped light-emitting device 80 according to Embodiment 2, and FIG.
13 shows an internal structure thereof. FIG. 14 shows the
light-distribution characteristic and illumination profile of the
wedge-shaped light-emitting device 80 of Embodiment 2. The wedge-shaped
light-emitting device 80 of Embodiment 2 is described with emphasis on
the difference between the wedge-shaped light-emitting device 80 of
Embodiment 2 and a mortar-shaped light-emitting device 50 of Embodiment
1.

[0153] FIG. 12 shows explanatory diagrams explaining the wedge-shaped
light-emitting device 80 according to Embodiment 2. (a) of FIG. 12 is a
plan view of the wedge-shaped light-emitting device 80 according to
Embodiment 2. (b) of FIG. 12 is a front view of the wedge-shaped
light-emitting device 80 according to Embodiment 2. (c) of FIG. 12 is a
side view of the wedge-shaped light-emitting device 80 according to
Embodiment 2.

[0154] FIG. 13 shows explanatory diagrams explaining the wedge-shaped
light-emitting device 80 according to Embodiment 2. (a) of FIG. 13 is a
plan view showing an internal structure of the wedge-shaped
light-emitting device 80 according to Embodiment 2. (b) of FIG. 13 is a
front view showing the internal structure of the wedge-shaped
light-emitting device 80 according Embodiment 2. (c) of FIG. 13 is a side
view of the wedge-shaped light-emitting device 80 according to Embodiment
2. (d) of FIG. 13 is an enlarged view of long LED chips 65 and an area
therearound in the wedge-shaped light-emitting device 80 according to
Embodiment 2. (e) of FIG. 13 is a plan view showing one long LED chip 65
being die-bonded to a position directly below the vertex 10c of the
letter V in the wedge-shaped light-emitting device 80 according to
Embodiment 2.

[0155] The wedge-shaped light-emitting device 80 has such features in
appearance that the sealing lens 10 has a quadrangular shape when viewed
planimetrically and has a concavely sunken part located above a
substantially central part of the substrate 20. The concavely sunken part
has a V-shaped cross-section (see the front view). Further, when viewed
in cross-section orthogonal to the V-shaped cross-section (see the side
view), the concavely sunken part has a concave shape with a flat bottom.
As a whole, the concavely sunken part forms a wedge-shaped groove.

[0156] It should be noted here that, as shown in (a) of FIG. 13, a total
of four LED chips 65 are die-bonded symmetrically about the bottom of the
letter V so that their longer sides are parallel to the V-shaped groove.
That is, the LED chips 65 are arranged so that the bottom of the letter V
extends directly above the center of a space area between two of the LED
chips 65 and the other two LED chips 65.

[0157] Such a configuration allows the position of the vertex 10c of the
letter V as viewed planimetrically in (d) of FIG. 13 to fall within the
space area 12b among the LED chips as shown in (d) of FIG. 13 so that the
four long LED chips 65 are arranged substantially evenly on either side
with respect to the wedge-shaped slope 10b and the vertex 10c, even if
the die-bonding position is slightly displaced along the x direction or
the y direction or, even if, in the case of molding of the sealing lens
10, the position of the vertex 10c of the wedge-shaped slope 10b is
slightly displaced along the x direction or the y direction. For this
reason, the resulting light-distribution characteristics of the
wedge-shaped light-emitting device 80 is stably high in symmetry.

[0158] The description here is given with reference to the four long LED
chips 65. However, the shape of each chip is not limited to such a long
shape. Further, it is possible to arrange a total of two LED chips with
one of them on the right side of the letter V and the other on the left
side, or arrange a total of six LED chips with three of them on the right
side of the letter V and the other three on the left side. In short, it
is only necessary to arrange LED chips in consideration of symmetry about
the wedge groove.

[0159] It should be noted that the wedge-shaped light-emitting device 80
may also be configured such that, as shown in (e) of FIG. 13, a single
LED chip 25, or a plurality of chips, is die-boned to a position directly
below the vertex 10c of the letter V. In this case, it is essential to
distribute light evenly on either side by strictly managing manufacturing
so that the center of the LED chip 25 is located directly below the
vertex 10c of the letter V. For this reason, the degree of difficulty
with which products of the same light-distribution characteristics are
stably produced is higher than in the case where the four long LED chips
65 are disposed evenly as shown in (a) of FIG. 13.

[0160] Further, due to problems of processing accuracy, it is difficult to
make the vertex 10c of the letter V in the form of an ideal vertex, and
the placement of an LED chip 25 as shown in (e) of FIG. 13 causes a
problem of leakage of light upward along the axis. For this reason, it is
especially preferable, for realization of stable characteristics in
production, that the mortar-shaped light-emitting device 50 be structured
such that such LED chips 25 as those shown in (a) of FIG. 13 are arrayed
in a position displaced from the vertex 10c.

[0161] FIG. 14 shows the light-distribution characteristics and
illumination profile of the wedge-shaped light-emitting device of
Embodiment 2. (a) of FIG. 14 is a simulation diagram three-dimensionally
showing the light-distribution characteristics of the wedge-shaped
light-emitting device according to Embodiment 2, and the intensity of
emitted light is indicated by the distance from the center 11a to an
outer edge surface 56. (b) of FIG. 14 is a simulation diagram showing the
illumination profile of the wedge-shaped light-emitting device 80
according to Embodiment 2.

[0162] The term "illumination profile" here means an illumination profile
obtained by illuminating a diffusing plate 112, and in (b) of FIG. 14,
the chain double-dashed line indicates a contour line 58. As shown in (b)
of FIG. 14, the illumination profile of the wedge-shaped light-emitting
device 80 forms a substantially rectangular and substantially oblong
illumination profile on the diffusing plate 112.

[0163] It should be noted that it is desirable, for the same reasons as
those stated in Embodiment 1, that the angle of inclination θ of
the wedge-shaped slope 10b range from an angle approximately equal to the
critical angle θc of total reflection to 60 degrees.

[0164] (Planar Light Source)

[0165] FIG. 15 shows a schematic diagram of a planar light source 200 of
Embodiment 2 and a pattern of arrangement of wedge-shaped light-emitting
devices. (a) of FIG. 15 is a side view of a display device including a
planar light source 200, a group of optical sheets 113 put on top of one
another, and a liquid crystal panel 150. (b) of FIG. 15 is a schematic
diagram showing correspondence between a wedge-shaped light-emitting
device 80 and its illumination profile. (c) of FIG. 15 is a plan view
showing an arrangement of wedge-shaped light-emitting devices 80 and the
illumination profiles of them as a planar light source.

[0166] The mortar-shaped light-emitting device 50, as shown (b) of FIG. 6,
has a substantially rectangular and substantially square illumination
profile. Such a simple square arrangement of mortar-shaped light-emitting
devices 50 in a pattern of arrangement in a planar light source 100 as
shown in (c) of FIG. 10 makes it easy to obtain a planar light source
that is high in in-plane uniformity of illuminance.

[0167] It should be noted that although the term "substantially
rectangular (rectangular shape)" encompasses a figure whose contour,
including the vertices, is rounded and curved. The term "curve"
encompasses a shape having a mixture of slightly outward concave and
convex curves smoothly combined, as seen from outside of the rectangular
shape.

[0168] On the other hand, the wedge-shaped light-emitting device 80, as
shown (b) of FIG. 14, has a substantially rectangular but substantially
oblong illumination profile. This makes it necessary to change the
pattern of arrangement of wedge-shaped light-emitting devices 80 as shown
in (c) of FIG. 15. Such a simple oblong arrangement of mortar-shaped
light-emitting devices 50 in accordance with the illumination profile
makes it easy to obtain a planar light source that is high in in-plane
uniformity of illuminance.

[0169] The group of optical sheets 113 includes first and second
unevenness eliminating sheets 113a and 113b put on top of each other.

[0170] As shown in (d) of FIG. 15, the first unevenness eliminating sheet
113a and the second unevenness eliminating sheet 113b are each a
translucent optical sheet having the same structure as that shown in
Embodiment 1. The luminance and color unevenness of light entering the
optical sheet are corrected along the direction along which convex shapes
are arrayed.

[0171] The first unevenness eliminating sheet 113a is placed so that the
longitudinal direction (referred to also as "busbar direction") of the
convex shapes of the first unevenness eliminating sheet 113a and the
direction of one side of the substantially rectangular illumination
profile of each of the wedge-shaped light-emitting devices are parallel
to each other, whereby luminance unevenness and color unevenness along
the X direction are uniformized. In practice, the first unevenness
eliminating sheet 113a is placed so that the longitudinal direction of
the convex shapes of the first unevenness eliminating sheet 113a and one
side of the rectangular contour of the sealing resin of each of the
wedge-shaped light-emitting devices 80 as seen from above are parallel to
each other. Alternatively, the first unevenness eliminating sheet 113a is
placed so that the longitudinal direction of the convex shapes of the
first unevenness eliminating sheet 113a and one side of the rectangular
contour of the mounting substrate 110 when the wedge-shaped
light-emitting devices 80 are seen from above are parallel to each other.
Alternatively, the first unevenness eliminating sheet 113a is placed so
that the longitudinal direction of the convex shapes of the first
unevenness eliminating sheet 113a and the X direction along which the
wedge-shaped light-emitting devices 80 are arrayed are parallel to each
other.

[0172] The second unevenness eliminating sheet 113b is placed on the first
unevenness eliminating sheet 113a so that the longitudinal direction of
the convex shapes of the second unevenness eliminating sheet 113b is
substantially perpendicular to the longitudinal direction of the convex
shapes of the first unevenness eliminating sheet 113a. That is, the
second unevenness eliminating sheet 113b is placed so that the
longitudinal direction of the convex shapes of the second unevenness
eliminating sheet 113b is parallel to the direction of another side of
the substantially rectangular illumination profile of each of the
wedge-shaped light-emitting devices 80 that is substantially
perpendicular to the above one side, whereby luminance unevenness and
color unevenness along the Y direction are uniformized.

[0173] It should be noted that luminance unevenness and color unevenness
along a diagonal direction across each substantially rectangular
illumination profile is uniformized by appropriately adjusting the
intervals at which the wedge-shaped light-emitting devices 80 are
arrayed, in addition to using the two unevenness eliminating sheets as
described above. This causes the luminance unevenness and the color
unevenness to be better uniformized by a combined effect of overlapping
of rectangular illumination patterns of wedge-shaped light-emitting
devices 80 adjacent to one another along the X direction, the Y
direction, and the diagonal direction.

[0174] Further, in order to guide light upward, it is possible to provide
luminance improving films 113c and 113d between the unevenness
eliminating sheets and the liquid crystal panel as mentioned above in
Embodiment 1.

[0175] Furthermore, it is possible to add a diffusing material to each of
the unevenness eliminating sheets.

[0176] It should be noted that the wedge-shaped light-emitting devices 80
may be replaced by light-emitting devices shown in embodiments other than
the present embodiment and each having a substantially rectangular
pattern of light emission. In such a case, the intervals at which the
light-emitting devices are arrayed are adjusted as needed.

[0177] Further, the substantially rectangular illumination profile may
have its corners slightly protruding diagonally, albeit not as protruding
diagonally as in the X-shaped illumination profile of the cloverleaf
light-emitting device 70 shown in (c) of FIG. 7. Alternatively, the
substantially rectangular illumination profile may be wholly rounded.

[0178] Each of the wedge-shaped light-emitting devices 80 of the present
embodiment may be configured such that the sunken part is a wedge-shaped
groove having its vertex facing the substrate and that the groove has a
V-shaped transverse cross-section.

[0179] Further, the wedge-shaped light-emitting device 80 may include a
plurality of long LED chips 65, and the plurality of long LED chips 65
may be arranged around a plane which is a symmetry plane of the wedge
shape and which extends through the bottom of the letter V.

[0180] Furthermore, the wedge-shaped light-emitting device 80 may include
two long LED chips 65 or a 2 multiple of long LED chips 65, and the two
long LED chips 65 or the 2 multiple of long LED chips 65 may be arranged
symmetrically at a distance from each other around a symmetry plane of
the wedge shape.

Embodiment 3

[0181] Another embodiment of the present invention is described below with
reference to FIGS. 16 and 17. It should be noted that the present
embodiment is identical in configuration to Embodiments 1 and 2 except
for that which is described in the present embodiment. Further, for
convenience of explanation, members having the same functions as those
shown in the drawings of Embodiment 1 and 2 are given the same reference
numerals and, as such, are not described below.

[0183] (a) of FIG. 16 is a plan view of the light-emitting device 90
according to Embodiment 3. (b) of FIG. 16 is a front view of the
light-emitting device 90 according to Embodiment 3. (c) of FIG. 16 is an
enlarged view of LED chips 25 and an area therearound in the
light-emitting device 90 according to Embodiment 3. (d) of FIG. 16 is a
plan view showing one LED chip being die-bonded to a position directly
below the vertex of the letter V in the light-emitting device 90
according to Embodiment 3.

[0184] The difference in appearance between the light-emitting device 90
and the wedge-shaped light-emitting device 80 of Embodiment 2 lies in the
shape of the concavely sunken part located in the central part of the
sealing lens 10. That is, the concavely sunken part of Embodiment 3 is
shaped as if concavely sunken parts of Embodiment 2 intersected crosswise
with each other.

[0185] It should be noted here that, as shown in (a) of FIG. 16, a total
of four LED chips 25 are die-bonded symmetrically about the bottom of the
letter V. Further, the LED chips 25 are arranged so that the bottom of
the cross extends directly above the centers of the space areas 12a and
12b among the LED chips 25.

[0186] Such a configuration allows the position of the vertex 10c of the
letter V as viewed planimetrically in (c) of FIG. 16 to fall within the
space areas 12a and 12b among the LED chips as shown in (c) of FIG. 16 so
that the four long LED chips 25 are arranged substantially evenly on
either side with respect to the wedge-shaped slope 10b and the vertex
10c, even if the die-bonding position is slightly displaced along the x
direction or the y direction or, even if, in the case of molding of the
sealing lens 10, the position of the vertex 10c of the wedge-shaped slope
10b is slightly displaced along the x direction or the y direction. For
this reason, the resulting light-distribution characteristics of the
wedge-shaped light-emitting device 90 is stably high in symmetry.

[0187] It should be noted that the light-emitting device 90 may also be
configured such that, as shown in (d) of FIG. 16, a single LED chip 25 is
die-bonded to a central part of the cross or a plurality of chips are
die-boned to a position directly below the vertex 10c of the letter V. In
this case, it is essential to distribute light evenly on either side by
strictly managing manufacturing so that the center of the LED chip 25 is
located directly below the vertex 10c of the letter V. For this reason,
the degree of difficulty with which products of the same
light-distribution characteristics are stably produced is higher than in
the case where the four long LED chips 25 are disposed evenly as shown in
(a) of FIG. 16.

[0188] Further, due to problems of processing accuracy, it is especially
preferable, for realization of stable characteristics in production, that
the light-emitting device 90 be structured such that such LED chips 25 as
those shown in (a) of FIG. 16 are arrayed in a position displaced from
the vertex 10c.

[0189] It should be noted that it is desirable, for the same reasons as
those stated in Embodiment 2, that the angle of inclination θ of
the wedge-shaped slope 10b range from an angle approximately equal to the
critical angle θc of total reflection to 60 degrees.

[0190] FIG. 17 shows the illumination profile of the light-emitting device
90 according to Embodiment 3. (a) of FIG. 17 is a simulation diagram
three-dimensionally showing the light-distribution characteristics of the
light-emitting device 90 according to Embodiment 3. (b) of FIG. 17 is a
simulation diagram showing the illumination profile of the light-emitting
device 90 according to Embodiment 3.

[0191] The light-emitting device 90, as shown (b) of FIG. 17, has a
substantially rectangular and substantially square illumination profile
on the diffusing plate 112. For this reason, as in the case of
mortar-shaped light-emitting devices 50, each of which forms a similar
illumination profile, a square arrangement of light-emitting devices 90
makes it easy to obtain a planar light source that is high in in-plane
uniformity of illuminance. It should be noted that although the term
"substantially rectangular (rectangular shape)" encompasses a figure
whose contour, including the vertices, is rounded and curved. The term
"curve" encompasses a shape having a mixture of slightly outward concave
and convex curves smoothly combined, as seen from outside of the
rectangular shape.

[0192] In the light-emitting device 90 according to the present
embodiment, the sunken parts each have its vertex pointing to the
substrate, and are each in the form of two wedge-shaped grooves
intersecting with each other and each having a V-shaped cross-section.

[0193] Further, the light-emitting device 90 may include a plurality of
LED chips 25 arranged symmetrically about a symmetry plane of each of the
wedge shapes.

[0194] Furthermore, the light-emitting device 90 may include four LED
chips 25 die-bonded at spaces coinciding with the vertices of the
V-shaped grooves as seen from the top surface 10a.

Embodiment 4

[0195] Another embodiment of the present invention is described below with
reference to FIGS. 18 and 19. It should be noted that the present
embodiment is identical in configuration to Embodiments 1 to 3 except for
that which is described in the present embodiment. Further, for
convenience of explanation, members having the same functions as those
shown in the drawings of Embodiments 1 to 3 are given the same reference
numerals and, as such, are not described below.

[0196] FIG. 18 shows explanatory diagrams explaining a light-emitting
device 190 according to Embodiment 4. (a) of FIG. 18 is a plan view of
the light-emitting device 190 according to Embodiment 4. (b) of FIG. 18
is a front view of the light-emitting device 190 according to Embodiment
4. (c) of FIG. 18 is a side view of the light-emitting device 190
according to Embodiment 4. (d) of FIG. 18 is a side view of the
light-emitting device 190 according to Embodiment 190 as seen from an
oblique angle of 45 degrees (from an angle θa).

[0197] FIG. 19 shows the light-distribution characteristics and
illumination profile of the light-emitting device 190 according to
Embodiment 4. (a) of FIG. 19 is a simulation diagram three-dimensionally
showing the light-distribution characteristics of the light-emitting
device 190 according to Embodiment 4. (b) of FIG. 19 is a simulation
diagram showing the illumination profile of the light-emitting device 190
according to Embodiment 4.

[0198] The light-emitting device 190 is different in appearance from the
light-emitting device 90 of Embodiment 3 in that, as shown in FIG. 18,
crossed V-shaped grooves formed in the sealing lens 10 each extend along
a diagonal direction from one vertex to the other.

[0199] Even such a shape makes it possible to form a substantially
rectangular and substantially square illumination profile on the
diffusing plate 112 as shown in FIG. 19. For this reason, as in the case
of mortar-shaped light-emitting devices 50, each of which forms a similar
illumination profile, a square arrangement of light-emitting devices 190
makes it easy to obtain a planar light source that is high in in-plane
uniformity of illuminance. It should be noted that although the term
"substantially rectangular (rectangular shape)" encompasses a figure
whose contour, including the vertices, is rounded and curved. The term
"curve" encompasses a shape having a mixture of slightly outward concave
and convex curves smoothly combined, as seen from outside of the
rectangular shape.

[0200] The light-emitting device 190 according to the present embodiment
is a light-emitting device including a substrate 20, LED chips 25
die-bonded to the substrate 20, and a wavelength conversion section 40
covering the LED chips 25. The wavelength conversion section 40 includes
surfaces composed of four planes standing upright with respect to the
substrate 20. The four planes are on all four sides to surround the
wavelength conversion section 40. The wavelength conversion section 40
has a ceiling side right opposite the substrate 20. On the ceiling side,
two wedge-shaped grooves each having its vertex pointing to the substrate
20 intersect with each other to diagonally connect four lines of
intersection formed by the four planes.

[0201] Since the light-emitting device 190 is thus configured such that
the two wedge-shaped grooves intersect with each other to diagonally
connect four lines of intersection formed by the four planes, the
light-emitting device 190 can emit light that forms a rectangular
illumination profile on a view plane parallel to the substrate 20. This
makes it possible to provide a light-emitting device structured to be
suited for a thin display device that has little illuminance unevenness
or chromaticity unevenness.

[0202] In the light-emitting device 190, the sealing body may contain an
LED package (wavelength conversion section) that absorbs primary light
emitted from the semiconductor light-emitting elements and emits
secondary light.

Embodiment 5

[0203] Another embodiment of the present invention is described below with
reference to FIG. 20. It should be noted that the present embodiment is
identical in configuration to Embodiments 1 to 4 except for that which is
described in the present embodiment. Further, for convenience of
explanation, members having the same functions as those shown in the
drawings of Embodiments 1 to 4 are given the same reference numerals and,
as such, are not described below.

[0204] FIG. 20 shows schematic diagrams showing an area active (local
dimming) liquid crystal display device 500. (a) of FIG. 20 is a plan view
of the area active (local dimming) liquid crystal display device 500. (b)
of FIG. 20 is a transverse cross-sectional view of the area active (local
dimming) liquid crystal display device 500 as taken along the line A-A'.

[0205] The area active (local dimming) liquid crystal display device 500
includes a liquid crystal display (hereinafter referred to as "display
panel") 510 and, as a backlight that illuminates the back surface of the
display panel 510, a planar light source 100 described in Embodiment 1.

[0206] The display panel 510 is a liquid crystal display panel that
controls light transmittance for each separate pixel, and is divided into
a plurality of regions including the plurality of pixels, and the planar
light source 100 is also divided into a plurality of regions
corresponding to those regions, with each of the regions configured to be
able to be driven independently. Furthermore, the planar light source 100
is driven by a driver (not illustrated) configured to be able to adjust
illuminance in accordance with an image that is displayed on the display
panel 510, and is configured to be able to selectively illuminate, i.e.,
to strongly illuminate the back surface of a high-illuminance region of
the image that is displayed on the display panel 510 and weakly
illuminate the back surface of a low-illuminance region of the image that
is displayed on the display panel 510. This makes it possible to reduce
power consumption and improve contrast.

[0207] (c) and (d) of FIG. 20 show a positional relationship between the
regions into which the display panel 510 has been divided and those into
which the planar light source 100 has been divided. Let it be assumed,
for example, that the display panel 510 displays an image taken of the
exit 512 of a tunnel from a vehicle traveling through the tunnel, with
the exit 512 seen in the vehicle's way. Then, the exit 512 of the tunnel
is displayed brightly in the dark. Let it be supposed that a region of
the display panel 510 where the exit 512 of the tunnel is displayed is a
segment 510a and a region of the planar light source 100 which faces the
back surface of the segment 510a is a segment 100a. In displaying such an
image, it is only necessary to increase the luminance of the segment 100a
facing the back surface of the segment 510a.

[0208] According to Embodiment 5, each of the mortar-shaped light-emitting
devices 50 disposed on the mounting substrate 110 exhibits a
substantially rectangular illumination profile and illuminates a limited
region having a substantially square shape. Therefore, only a negligible
amount of light diffuses into regions other than the region. This makes
it possible to reduce crosstalk where light leaks into an adjacent
segment. Therefore, a planar light source mounted with mortar-shaped
light-emitting devices 50 can be suitably used as a backlight of an area
active (local dimming) display device.

[0209] It should be noted that the planar light source is not limited to
that described in Embodiment 1, and may be that described in Embodiment
2, 3, or 4. Further, the display device is not limited to a liquid
crystal display device, and only needs to be a general display device
that varies in light transmittance from region to region.

[0210] A planar light source of the present invention includes: a mounting
substrate; and a plurality of light-emitting devices as described in any
one of the embodiments, the plurality of light-emitting devices being
arrayed on the mounting substrate to serve as the planar light source,
the light-emitting devices being arrayed in such a way as to form
respective rectangular illumination profiles having sides parallel to one
another. This makes it possible to provide a planar light source
structured to be suitable for a thin display device that has little
illuminance unevenness or chromaticity unevenness.

[0211] A display device of the present invention includes: a planar light
source described above; and a display panel that varies in light
transmission from region to region, the planar light source illuminating
the back surface of the display panel. This makes it possible to provide
a thin display device that has little illuminance unevenness or
chromaticity unevenness.

[0212] The present invention is not limited to the description of the
embodiments above. For example, it is self-evident that although the
sealing resin has been described as having a substantially square shape
as viewed planimetrically, the sealing resin cannot be prevented from
having a substantially oblong shape as viewed planimetrically. That is,
the present invention may be altered within the scope of the claims. An
embodiment based on a proper combination of technical means disclosed in
different embodiments is encompassed in the technical scope of the
present invention.

[0213] In the embodiments above, area active (local dimming) driving
results in great interference between one region and another. Therefore,
it is OK to replace a light-emitting device of any of the embodiments
above with a light-emitting device having an illumination profile, based
on a rectangular illumination profile in the form of a square or an
oblong shape, which has its vertices slightly protruding diagonally,
although it is not desirable that the vertices too greatly protrude
diagonally as in the illumination profile of a comparative example of a
cloverleaf light-emitting device 70.

Additional Embodiment 1

[0214] The present embodiment is a modification of Embodiment 1 of (a)
through (d) of FIG. 2 and (a) through (d) of FIG. 4.

[0215] This modification differs from Embodiment 1 in that the substrate
20 has an oblong shape, that the opening in the mortar-shaped slope 10b
(i.e., the junction between the ceiling surface 10a and the slope 10b),
when viewed planimetrically, has an oval or elliptic shape that extends
along the longer sides of the substrate 20, and that the wavelength
conversion section 40, when viewed planimetrically, has its edge in an
oval shape that falls within the opening.

[0216] FIG. 22 shows a top view and a side view of an example where the
opening has an elliptic shape in a light-emitting device according to
this modification.

Additional Embodiment 2

[0217] FIG. 23 shows a top view and a side view of the present
light-emitting device.

[0218] The present embodiment is a modification of Embodiment 2 of (a)
through (d) of FIG. 13.

[0219] As with Additional Embodiment 1, the present embodiment is a case
example where the substrate 20 has an oblong shape, where the opening in
the wedge-shaped slope (i.e., the junction between the ceiling surface
10a and the slope 10b), when viewed planimetrically, has an elliptic
shape that extends along the longer sides of the substrate 20, and where
the wavelength conversion section 40, when viewed planimetrically, has
its edge in an oval shape that falls within the opening. The wedge-shaped
slope has both of its ends in a surface shape of a halved inverted cone.

[0220] In the embodiments above, light-emitting devices each having a
rectangular illumination profile in the form of a square or an oblong
shape on a view plane parallel to the substrate and a planar light source
constituted by such light-emitting devices have been described. It should
be noted, however, that the rectangular illumination profile needs only
be such a shape that a surface is filled with light-emitting patterns
with no space therebetween, and may for example be triangular,
hexangular, or octangular.

General Overview of Embodiments

[0221] The planar light source 100 and 200 may each be configured such
that the first intervals and the second intervals are equal.

[0222] The planar light source 100 and 200 may each be configured such
that the first intervals are shorter than the second intervals.

[0223] The planar light source 100 and 200 may each be configured such
that the direction in which the light sources each emit light of maximum
intensity and the vertical direction form an angle of 30 degrees or
larger to 50 degrees or smaller.

[0224] The planar light source 100 and 200 may each be configured such
that on a virtual viewing plane parallel to the mounting substrate 110,
the light sources each has a contour of an illumination profile in a
rectangular shape with rounded vertices.

[0225] The planar light source 100 and 200 may each be configured such
that the illumination profile has one side parallel or substantially
parallel to the first direction.

[0226] The planar light source 100 and 200 may each be configured such
that the first intervals are each 15 mm or longer and a value obtained by
dividing each of the distance by each of the first intervals is smaller
than 0.7.

[0227] The planar light source 100 may be configured such that each of the
light sources is a light source including: a substrate 20; an LED chip 25
die-bonded to the substrate 20; and a lens covering the LED chip 25, the
lens including (i) four surfaces 13a to 13d standing upright with respect
to the substrate 20 and (ii) a top surface 10a right opposite the
substrate 20, the top surface 10a having a concavely sunken part formed
therein.

[0228] The planar light source 200 may be configured such that each of the
light sources is a light source including: a substrate 20; an long LED
chip 65 die-bonded to the substrate 20; and a lens covering the long LED
chip 65, the lens including (i) four surfaces 13a to 13d standing upright
with respect to the substrate 20 and (ii) a top surface 10a right
opposite the substrate 20, the top surface 10a having a concavely sunken
part formed therein.

[0229] The planar light source 100 may be configured such that the lens
serves as a sealing body that seals in the LED chip 25.

[0230] The planar light source 200 may be configured such that the lens
serves as a sealing body that seals in the long LED chip 65.

[0231] The planar light source 100 and 200 may each be configured such
that the sunken part has a circular conical shape, a truncated circular
conical shape, a polygonal conical shape, or a truncated polygonal
conical shape having its vertex pointing to the substrate 20.

[0232] The planar light source 100 may be configured such that the LED
chip 25 is placed in an area around a central axis of the sunken part.

[0233] The planar light source 200 may be configured such that the long
LED chip 65 is placed in an area around a central axis of the sunken
part.

[0234] The planar light source 100 may further include a wavelength
conversion section 40, sandwiched between the LED chip 25 and the lens,
which covers the LED chip 25, the wavelength conversion section 40 being
composed of a resin layer containing a fluorescent substance dispersed in
advance therein, the fluorescent substance absorbing primary light
emitted from the LED chip 25 and emitting secondary light.

[0235] The planar light source 200 may further include a wavelength
conversion section 40, sandwiched between the long LED chip 65 and the
lens, which covers the long LED chip 65, the wavelength conversion
section 40 being composed of a resin layer containing a fluorescent
substance dispersed in advance therein, the fluorescent substance
absorbing primary light emitted from the long LED chip 65 and emitting
secondary light.

[0236] A display device according to the present embodiment includes a
planar light source 100 and a liquid crystal panel 150 that varies in
light transmission from one pixel to another, and the planar light source
100 illuminates the back surface of the liquid crystal panel 150. This
makes it possible to provide a thin display device that has little
illuminance unevenness or chromaticity unevenness.

[0237] A display device according to the present embodiment includes a
planar light source 200 and a liquid crystal panel 150 that varies in
light transmission from one pixel to another, and the planar light source
200 illuminates the back surface of the liquid crystal panel 150. This
makes it possible to provide a thin display device that has little
illuminance unevenness or chromaticity unevenness.

[0238] The foregoing display devices are both configured such that: the
liquid crystal panel 150 is configured to be able to be driven for each
separate region including the plurality of pixels; and the planar light
source 100 or 200 is configured such that its luminance is able to be
adjusted for each separate region including the plurality of pixels.

INDUSTRIAL APPLICABILITY

[0239] The present invention is used as a light source for use in a
backlight that illuminates the back surface of a liquid crystal display
panel. Further, the present invention is used as a light source for use
in a backlight suitable for an area active (local dimming) liquid crystal
display device. Furthermore, the present invention can be applied to a
lighting apparatus.